When the system boots, it reads the current values into memory, creating active values. An active value remains equal to the current value until you change either the active value or the current value.

When you execute the AUTOGEN command procedure through the SETPARAMS phase, it changes current values.

The System Management utility (SYSMAN) and the System Generation utility (SYSGEN) allow you to show and modify both current and active values. Use the USE and WRITE commands to specify which values you want to show or modify.

For more information about managing parameters with SYSMAN, see Section 1.7. For more information about managing parameters with SYSGEN, see Section 1.8.

On VAX systems, the operating system allocates and deallocates memory for processes in units called pages. A page on a VAX system is 512 bytes. Some system parameter values are allocated in units of pages.

On Alpha systems, some system parameter values are allocated in units of pages, while others are allocated in units of pagelets.

A page on an Alpha system can be 8 kilobytes (KB) (8192 bytes), 16 KB, 32 KB, or 64 KB. A page let is a 512-byte unit of memory. One Alpha pagelet is the same size as one VAX page. On an Alpha computer with a page size of 8 KB, 16 Alpha pagelets equal one Alpha page.

When reviewing parameter values, especially those parameters related to memory management, be sure to note the units required for each parameter. Section 1.7.2 and Section 1.8.2 explain how to show parameter values and their units of allocation.

AUTOGEN feedback minimizes the need for you to modify parameter values or system file sizes. Instead, feedback allows AUTOGEN to automatically size the operating system based on your actual work load. Sizing is the process of matching the allocation of system resources (memory and disk space) with the workload requirements of your site.

Feedback is information, continuously collected by the operating system executive, about the amount of various resources the system uses to process its work load. The information is collected when exception events occur, so the collection does not affect system performance. When run in feedback mode, AUTOGEN analyzes this information and adjusts any related parameter values.

AUTOGEN feedback affects the following resources (for a complete list of the affected system parameters, refer to the VSI OpenVMS System Management Utilities Reference Manual):

Feedback is gathered during AUTOGEN's SAVPARAMS phase and is written to the file SYS$SYSTEM:AGEN$FEEDBACK.DAT. This file is then read during the GETDATA phase. (See Section 1.4.3 for more information about AUTOGEN phases.)

Feedback is useful only if it accurately reflects the system's normal work load. For this reason, AUTOGEN performs some basic checks on the feedback and issues a warning message for either of the following conditions:

Whenever you modify the system (for example, a hardware upgrade, a change in the number of users, an optional product installation), you should operate in the new system environment for a period of time, and then execute AUTOGEN again starting from the SAVPARAMS phase.

On VAX systems, you can define the logical name AGEN$FEEDBACK_REQ_TIME to specify, in hours, a minimum age required for feedback. For more information, see Section 1.5.2.

When AUTOGEN runs, it displays whether feedback is used, as follows:

Feedback information was collected on 21-JAN-2016 14:00:08.53
Old values below are the parameter values at the time of collection.
The feedback data is based on 21 hours of up time.
Feedback information will be used in the subsequent calculations

Decides whether to use the system parameter values and system file sizes calculated by AUTOGEN. To help in your decision making, AUTOGEN generates a report file (SYS$SYSTEM:AGEN$PARAMS.REPORT) that includes the following information:

Example 1.1 shows the contents of a sample AUTOGEN feedback report for a VAX system. On Alpha systems, the feedback report is similar but not identical to this example.

Suppressing Informational Messages

To suppress the display of informational messages, define the AGEN$REPORT_NO_INFORMATIONALS logical to TRUE. Messages are entered in SYS$SYSTEM:AGEN$PARAMS.REPORT regardless of the value of AGEN$REPORT_NO_INFORMATIONALS.

Filtering DCL Statements from Your Report

The feedback report will contain DCL statements in MODPARAMS.DAT that are not simple assignments to system parameters or the ADD_, MAX_, or MIN_ extensions. To filter these statements out of the report, begin each statement in MODPARAMS.DAT with a dollar sign ($).

AUTOGEN Parameter Calculation Report on node: NODE22
  This information was generated at 23-APR-2016 01:45:47.87
  AUTOGEN was run from GETDATA to TESTFILES using FEEDBACK

** No changes will be done by AUTOGEN **
   The values given in this report are what AUTOGEN would
    have set the parameters to.

Processing Parameter Data files
-------------------------------

** WARNING ** - The system was up for less than 24 hours when the feedback
information was recorded. This could result in feedback information
that does not accurately reflect your typical work load.

Including parameters from: SYS$SYSTEM:MODPARAMS.DAT
The following was detected within MODPARAMS.DAT
   Please review immediately.

** INFORMATIONAL ** - Multiple MIN values found for MIN_CHANNELCNT.
 Using MODPARAMS value (550) which is superseding OpenVMS value (255)

** INFORMATIONAL ** - Multiple MIN values found for MIN_SWPOUTPGCNT.
 Using MODPARAMS value (1000) which is superseding OpenVMS value (500)

** INFORMATIONAL ** - Multiple MIN values found for MIN_PQL_DWSEXTENT.
 Using MODPARAMS value (11000) which is superseding OpenVMS value (1024)

** INFORMATIONAL ** - Multiple MIN values found for MIN_PQL_MWSEXTENT.
 Using MODPARAMS value (11000) which is superseding OpenVMS value (1024)
Feedback information was collected on 22-APR-2016 14:00:07.70
  Old values below are the parameter values at the time of collection.
  The feedback data is based on 13 hours of up time.
  Feedback information will be used in the subsequent calculations


Parameter information follows:
------------------------------

MAXPROCESSCNT parameter information:
 Feedback information.
    Old value was 100, New value is 80
    Maximum Observed Processes: 52

Information about VMS executable image Processing:

 Processing SYS$MANAGER:VMS$IMAGES_MASTER.DAT


GBLPAGFIL parameter information:
 Override Information - parameter calculation has been overridden.
    The calculated value was 1024.  The new value is 6024.
    GBLPAGFIL has been increased by 5000.
    GBLPAGFIL is not allowed to be less than 6024.


GBLPAGES parameter information:
 Feedback information.
    Old value was 43300, New value is 50000
    Peak used GBLPAGES: 36622
    Global buffer requirements: 6024


GBLSECTIONS parameter information:
 Feedback information.
    Old value was 400, New value is 400
    Peak used GBLSECTIONS: 294
 Override Information - parameter calculation has been overridden.
    The calculated value was 350.  The new value is 400.
    GBLSECTIONS is not allowed to be less than 400.

LOCKIDTBL parameter information:
 Feedback information.
    Old value was 2943, New value is 3071
    Current number of locks: 1853
    Peak number of locks: 3200

LOCKIDTBL_MAX parameter information:
 Feedback information.
    Old value was 65535, New value is 65535

RESHASHTBL parameter information:
 Feedback information.
    Old value was 1024, New value is 1024
    Current number of resources: 957

MSCP_LOAD parameter information:
 Override Information - parameter calculation has been overridden.
    The calculated value was 1.  The new value is 0.
    MSCP_LOAD has been disabled by a hard-coded value of 0.

MSCP_BUFFER parameter information:
 Feedback information.
    Old value was 128, New value is 128
    MSCP server I/O rate: 0 I/Os per 10 sec.
    I/Os that waited for buffer space: 0
    I/Os that fragmented into multiple transfers: 0

SCSCONNCNT parameter information:
 Feedback information.
    Old value was 5, New value is 5
    Peak number of nodes: 1
    Number of CDT allocation failures: 0

SCSRESPCNT parameter information:
 Feedback information.
    Old value was 300, New value is 300
    RDT stall count: 0

SCSBUFFCNT parameter information:
 Feedback information.
    Old value was 512, New value is 512
    CIBDT stall count: 0


NPAGEDYN parameter information:
 Feedback information.
    Old value was 686592, New value is 783360
    Maximum observed non-paged pool size: 815616 bytes.
    Non-paged pool request rate: 47 requests per 10 sec.


LNMSHASHTBL parameter information:
 Feedback information.
    Old value was 1024, New value is 1024
    Current number of shareable logical names: 1194


ACP_DIRCACHE parameter information:
 Feedback information.
    Old value was 88, New value is 88
    Hit percentage: 99%
    Attempt rate: 0 attempts per 10 sec.

ACP_DINDXCACHE parameter information:
 Feedback information.
    Old value was 25, New value is 25
    Hit percentage: 97%
    Attempt rate: 1 attempts per 10 sec.

ACP_HDRCACHE parameter information:
 Feedback information.
    Old value was 88, New value is 106
    Hit percentage: 98%
    Attempt rate: 17 attempts per 10 sec.

ACP_MAPCACHE parameter information:
 Feedback information.
    Old value was 8, New value is 8
    Hit percentage: 2%
    Attempt rate: 4 attempts per 10 sec.

PAGEDYN parameter information:
 Feedback information.
    Old value was 521728, New value is 542208
    Current paged pool usage: 304160 bytes.
    Paged pool request rate: 1 requests per 10 sec.

PFRATL parameter information:
 Override Information - parameter calculation has been overridden.
    The calculated value was 0.  The new value is 1.
    PFRATL has been disabled by a hard-coded value of 1.

WSDEC parameter information:
 Override Information - parameter calculation has been overridden.
    The calculated value was 35.  The new value is 19.
    WSDEC has been disabled by a hard-coded value of 19.

MPW_LOLIMIT parameter information:
 Override Information - parameter calculation has been overridden.
    The calculated value was 120.  The new value is 2100.
    MPW_LOLIMIT is not allowed to be less than 2100.

MPW_HILIMIT parameter information:
 Override Information - parameter calculation has been overridden.
    The calculated value was 1310.  The new value is 4500.
    MPW_HILIMIT is not allowed to be less than 4500.

LONGWAIT parameter information:
 Override Information - parameter calculation has been overridden.
    The calculated value was 30.  The new value is 10.
    LONGWAIT has been disabled by a hard-coded value of 10.


WSMAX parameter information:
 Override Information - parameter calculation has been overridden.
    The calculated value was 8200.  The new value is 12000.
    WSMAX is not allowed to be less than 12000.


PROCSECTCNT parameter information:
 Override Information - parameter calculation has been overridden.
    The calculated value was 32.  The new value is 40.
    PROCSECTCNT is not allowed to be less than 40.


PQL_DWSEXTENT parameter information:
 Override Information - parameter calculation has been overridden.
    The calculated value was 400.  The new value is 11000.
    PQL_DWSEXTENT is not allowed to be less than 11000.


PQL_MWSEXTENT parameter information:
 Override Information - parameter calculation has been overridden.
    The calculated value was 2048.  The new value is 11000.
    PQL_MWSEXTENT is not allowed to be less than 11000.

VAXCLUSTER parameter information:
 Override Information - parameter calculation has been overridden.
    The calculated value was 1.  The new value is 0.
    VAXCLUSTER has been disabled by a hard-coded value of 0.

Page, Swap, and Dump file calculations

  Page and Swap file calculations.

PAGEFILE1_SIZE parameter information:
 Feedback information.
    Old value was 45200, New value is 50500
    Maximum observed usage: 25265
 PAGEFILE1_SIZE will be modified to hold 50500 blocks

PAGEFILE2_SIZE parameter information:
 Feedback information.
    Old value was 154000, New value is 194400
    Maximum observed usage: 97175
 PAGEFILE2_SIZE will be modified to hold 194400 blocks

 ** WARNING ** - The disk on which PAGEFILE2 resides would be
    over 95% full if it were modified to hold 194400 blocks.
    NODE22$DKA300:[SYSTEM_FILES]PAGEFILE.SYS will not be modified.
    NODE22$DKA300:[SYSTEM_FILES]PAGEFILE.SYS will remain at 154002 blocks.

SWAPFILE1_SIZE parameter information:
 Feedback information.
    Old value was 15000, New value is 15000
    Maximum observed usage: 14280
 Override Information - parameter calculation has been overridden.
    The calculated value was 21400.  The new value is 15000.
    SWAPFILE1_SIZE is not allowed to exceed 15000.
 SWAPFILE1 will not be modified.

SWAPFILE2_SIZE parameter information:
 Feedback information.
    Old value was 50000, New value is 26300
    Maximum observed usage: 1680
 SWAPFILE2_SIZE will be modified to hold 26300 blocks

 ** WARNING ** - The disk on which SWAPFILE2 resides would be
    over 95% full if it were modified to hold 26300 blocks.
    NODE22$DKA300:[SYSTEM_FILES]SWAPFILE.SYS will not be modified.
    NODE22$DKA300:[SYSTEM_FILES]SWAPFILE.SYS will remain at 50001 blocks.


  Dumpfile calculations:

 No dump file modifications would have been made.
 Dumpfile will remain at 34116 blocks.

When you invoke AUTOGEN, you specify a start phase and an end phase for AUTOGEN to execute. AUTOGEN executes all phases from the start phase to the end phase. Depending on the start phase and end phase you specify, AUTOGEN can execute any of the following phases, in the order shown in Table 1.2.

For detailed information about each AUTOGEN phase and the files affected by each phase, refer to the VSI OpenVMS System Management Utilities Reference Manual.

AUTOGEN reads a parameter file named MODPARAMS.DAT during the GETDATA phase. You can add commands to this file to control the system parameter values and file sizes that AUTOGEN sets. You can use MODPARAMS.DAT to perform the following actions:

To help track changes you make to MODPARAMS.DAT, make sure you add comments, preceded by the exclamation point (!), each time you change the file.

Example

The following example shows the contents of a sample MODPARAMS.DAT file:

!
! ***************** A Sample MODPARAMS.DAT for Node NODE22 ***************
!
! MODPARAMS.DAT for "NODE22"
! REVISED: 04/29/00 -CHG- Upped GBLPAGES to account for ADA.
!
SCSNODE         = "NODE22"      ! This is not calculated by AUTOGEN.
SCSSYSTEMID     = 19577         ! This is not calculated by AUTOGEN.
TTY_DEFCHAR2    = %X0D34        ! This is not calculated by AUTOGEN.
ADD_ACP_DIRCACHE= 150           ! Hit rate was only 65% on directory cache.
MIN_PAGEDYN     = 500000        ! PAGEDYN must be at least 1/2 Mbyte to
                                ! account for a large number of logical names.
!

MAX_PAGEFILE1_SIZE  = 15000     ! Maximum size for primary page.
MAX_SWAPFILE        =  5000     ! Maximum size for swap file space.
MAX_DUMPFILE        = 32768     ! Maximum size for dump file space.

ADD_GBLPAGES    = 425+507+157   ! Account for MCS, BLISS32 and ADA.
ADD_GBLSECTIONS = 4 + 5 + 2     ! Account for MCS, BLISS32 and ADA.
VIRTUALPAGECNT  = 144264        ! So that we can read MONSTR's 68Mb dumps.
!
! end of MODPARAMS.DAT for NODE22 

If, after examining the AGEN$PARAMS.REPORT or SETPARAMS.DAT file, you decide to correct hardware configuration data or modify system parameter values chosen by AUTOGEN, edit the MODPARAMS.DAT file as described in this section to manually specify parameter values.

For information about editing MODPARAMS.DAT to control sizes of page, swap, and dump files, see Section 2.15.1.2.

You can define symbols in MODPARAMS.DAT using the following formats to control parameter values:

When defining symbols in MODPARAMS.DAT, make sure of the following data:

To help track changes you make to MODPARAMS.DAT, make sure you add comments preceded by an exclamation point (!) each time you change the file.

ADD_GBLPAGES=500
ADD_NPAGEDYN=10000

MIN_PAGEDYN = 400000

MAX_PAGEDYN = 400000

parameter = parameter-value ! comment

SCSNODE = "BIGVAX"   ! the node name 

NUM_NODES = 30

NUM_ETHERADAPT = 40 

On VAX systems, AUTOGEN feedback is useful only when a system has been running long enough to accurately reflect the system's normal work load. By default, AUTOGEN uses feedback if the data is older than 24 hours. On VAX systems, you can define the logical name AGEN$FEEDBACK_REQ_TIME to specify, in hours, a different minimum age required for feedback. AUTOGEN uses this value to determine whether the feedback is to be used.

For example, you might define the logical name as follows, to indicate that AUTOGEN should use feedback if it is older than 19 hours:

$ DEFINE/SYSTEM AGEN$FEEDBACK_REQ_TIME 19

To define this logical name each time the system starts up, add this command to SYLOGICALS.COM.

You can include external parameter files in MODPARAMS.DAT. For example, you might want to set a system parameter to the same value on all nodes in a VAXcluster or an OpenVMS Cluster environment; you might also want to specify node-specific values for other system parameters. You could specify the cluster-common values in a separate cluster-common file and include this cluster-common file in the MODPARAMS.DAT file on each system in the cluster.

To include a parameter file, place a command in the following format in MODPARAMS.DAT, or in any parameter file that is included in MODPARAMS.DAT:

AGEN$INCLUDE_PARAMS full-directory-spec:filename

Example

SYS$COMMON:[SYSEXE]CLUSTERPARAMS.DAT

Add the following line in the MODPARAMS.DAT file in the system-specific directory of each cluster:

AGEN$INCLUDE_PARAMS SYS$COMMON:[SYSEXE]CLUSTERPARAMS.DAT

The contents of MODPARAMS.DAT are evaluated as DCL statements; you can make assignments to symbols with names that are not system parameters (for example, scratch variables or conditional assignments based on other values). Traditionally, every such assignment is logged in AGEN$PARAMS.REPORT, sometimes creating a large file with many logging statements that do not interest users.

You can prefix any assignments that you prefer not to log in AGEN$PARAMS.REPORT with a dollar sign ($). When AUTOGEN encounters a MODPARAMS.DAT record beginning with a dollar sign, it does not check the list of known system parameters and does not log this record to AGEN$PARAMS.REPORT.

If the command procedure report described in Section 1.6 shows AUTOGEN's calculations are different from the current values, correct the tuning by executing AUTOGEN with one of the two following commands:

It helps to understand the different system parameter values explained in Section 1.1.1. Briefly, current values are stored in the default parameter file on disk. Active values are stored in memory and are used while the system is running. In addition to these values, SYSMAN writes a temporary copy into its own work area on disk. Figure 1.2 illustrates these different sets of values and how SYSMAN commands affect them. In this figure:

During a typical session, you can display and change values in the following sequence:

For a list of all the system parameters, refer to the VSI OpenVMS System Management Utilities Reference Manual.

Use the SYSMAN command PARAMETERS SHOW to display parameter values for all the nodes in a cluster.

Examples

Use the SYSMAN command PARAMETERS WRITE to write system parameter values and the name of the site-independent startup command procedure to your choice of parameter file or the current system parameter file on disk.

The PARAMETERS WRITE CURRENT command sends a message to OPCOM to record the event, unless you have changed the system message format with the DCL command SET MESSAGE.

Examples

Using the SYSMAN commands PARAMETERS SET, PARAMETERS WRITE, and PARAMETERS USE enables you to modify active parameter values.

Modifying active values immediately affects dynamic parameters by changing their values in memory. Appendix C of the VSI OpenVMS System Management Utilities Reference Manual identifies dynamic parameters, as does the SYSMAN command PARAMETERS SHOW/DYNAMIC. Values for nondynamic parameters cannot be changed while the system is running.

Modifying active values does not affect current values in the system parameter file on disk, because the next time you boot the system, the values on disk are established as the active values.

If you set new active parameter values and you want to use the new values for subsequent boot operations, write the new values to the current parameter file with the PARAMETERS WRITE CURRENT command, as shown in the Examples section.

Examples

You should understand the different system parameter values explained in Section 1.1.1. Briefly, CURRENT values are stored in the default parameter file on disk, and are used to establish initial parameter values when the system boots. ACTIVE values are stored in memory and are used while the system is running. In addition to these values, SYSGEN writes a temporary copy into its own work area on disk. Figure 1.3 illustrates these different sets of values and shows how SYSGEN commands affect them.

For a list of all the system parameters, refer to the VSI OpenVMS System Management Utilities Reference Manual.

For more information about the SYSGEN SHOW command and qualifiers, refer to the VSI OpenVMS System Management Utilities Reference Manual.

Example

$ RUN SYS$SYSTEM:SYSGEN
SYSGEN> USE CURRENT
SYSGEN> SHOW/TTY

Parameters in use: Current
Parameter Name   Current    Default     Min.      Max. Unit       Dynamic
--------------   -------    -------  -------  -------  ----       -------
                                                   
TTY_SCANDELTA   10000000   10000000  100000        -1  100Ns
TTY_DIALTYPE           0          0       0       255  Bit-Encode
TTY_SPEED             15         15       1        16  Special
TTY_RSPEED             0          0       0        16  Special
TTY_PARITY            24         24       0       255  Special
TTY_BUF               80         80       0     65535  Characters
TTY_DEFCHAR    402657952  402657952       0        -1  Bit-Encode
TTY_DEFCHAR2      135178       4098       0        -1  Bit-Encode
TTY_TYPAHDSZ          78         78       0        -1  Bytes
TTY_ALTYPAHD        2048        200       0     32767  Bytes
TTY_ALTALARM         750         64       0        -1  Bytes
TTY_DMASIZE           64         64       0        -1  Bytes       D 
TTY_CLASSNAME      "TTY"      "TTY"    "AA"      "ZZ"  Ascii
TTY_SILOTIME           8          8       0       255  Ms
TTY_TIMEOUT         3600        900       0        -1  Seconds     D
TTY_AUTOCHAR           7          7       0       255  Character   D
SYSGEN>
Parameters in use: Current

Modifying the current values in the default system parameter file has no immediate effect on active values on a running system. However, during subsequent boot operations, the system is initialized with the new values.

Example

$ SET DEFAULT SYS$SYSTEM
$ RUN SYSGEN
SYSGEN> USE CURRENT
SYSGEN> SET TTY_TIMEOUT 3600
SYSGEN> WRITE CURRENT
SYSGEN> EXIT

Modifying active values immediately affects dynamic parameters by changing their values in memory. VSI OpenVMS System Management Utilities Reference Manual identifies dynamic parameters (as does the SYSGEN command SHOW/DYNAMIC). You cannot change values for non dynamic parameters while the system is running.

Modifying active values does not affect the current values in the system parameter file on disk. The next time you boot the system, the old current values are established as the active values.

If you set new active parameter values (by entering WRITE ACTIVE) and you want to use the new values for subsequent boot operations, you must write the new values to the current parameter file on disk by entering the WRITE CURRENT command, as explained in Section 1.8.3. If the parameters are not dynamic parameters, you must enter the WRITE CURRENT command and reboot the system.

Examples

Creating a new parameter file has no effect on the running system. During a subsequent conversational boot operation, however, you can initialize the active system with the values of the new file.

How to Perform This Task

Examples

The operating system uses the latest version of SYS$SYSTEM:SYSDUMP.DMP to store system crash dumps. If SYSDUMP.DMP does not exist in SYS$SYSTEM, the operating system uses the system page file, SYS$SYSTEM:PAGEFILE.SYS, overwriting the contents of that file.

If the SAVEDUMP system parameter is set, the crash dump is retained in PAGEFILE.SYS when the system is booted. If SAVEDUMP is clear, the system uses the page file for paging; any dump written to the page file is lost.

For detailed instructions, see Section 2.12.

Requirements for Creating a Useful System Dump

BACKUP Considerations

A system dump file has the NOBACKUP attribute; therefore, the Backup utility (BACKUP) does not copy the file unless you use the qualifier /IGNORE=NOBACKUP when invoking BACKUP. When you use the SDA COPY command to copy the system dump file to another file, the operating system does not automatically set the new file to NOBACKUP. If you want to set the NOBACKUP attribute on the copy, use the SET FILE command with the /NOBACKUP qualifier as described in the VSI OpenVMS DCL Dictionary.

Security Considerations

By default, SYS$SYSTEM:SYSDUMP.DMP is protected against world access. Because a system dump file can contain privileged information, you should keep this level of protection on system dump files. Similarly, when you copy system dump files using the System Dump Analyzer utility (SDA) as explained in Section 2.10 and Section 2.12, be sure to protect the copy from world read access. For more information about file protection, refer to the VSI OpenVMS Guide to System Security.

Sufficient space in the system dump file is critical to saving a complete crash dump. The AUTOGEN command procedure calculates an appropriate size for your system dump file. However, if you want to manually calculate the system dump file size, use the following formula, which calculates the file size required to hold a physical dump.

For SYSDUMP.DMP

size-in-blocks(SYS$SYSTEM:SYSDUMP.DMP)
= size-in-pages(physical-memory)
+ number-of-error-log-buffers * blocks-per-buffer
+ 1

size-in-blocks(SYS$SYSTEM:SYSDUMP.DMP)
= size-in-pages(physical-memory) * blocks-per-page
+ number-of-error-log-buffers * blocks-per-buffer
+ 10

$ PAGESIZE==F$GETSYI ("PAGE_SIZE")
$ BLOCKSPERPAGE=PAGESIZE/512
$ SHOW SYMBOL BLOCKSPERPAGE

A large memory system or a system with small disk capacity might not be able to supply enough disk space for a full memory dump. Under these circumstances, you should set the system parameter DUMPSTYLE to the appropriate value to indicate that the system is to dump only selective information. For more information, see Section 2.5.

For PAGEFILE.SYS

If SYS$SYSTEM:SYSDUMP.DMP does not exist, the system writes crash dumps to the primary page file SYS$SYSTEM:PAGEFILE.SYS. The AUTOGEN command procedure calculates an appropriate size for your page file. However, to manually calculate the minimum page file size required to hold crash dumps, use the following formula:

size-in-blocks(SYS$SYSTEM:PAGEFILE.SYS)
= size-in-pages(physical-memory)
+ number-of-error-log-buffers * blocks-per-buffer
+ 1
+ 1000

size-in-blocks(SYS$SYSTEM:PAGEFILE.SYS)
= size-in-pages(physical-memory) * blocks-per-page
+ number-of-error-log-buffers * blocks-per-buffer
+10
+ value of the system parameter RSRVPAGCNT

$ PAGESIZE==F$GETSYI ("PAGE_SIZE")
$ BLOCKSPERPAGE=PAGESIZE/512
$ SHOW SYMBOL BLOCKSPERPAGE

These calculations differ on OpenVMS VAX and Alpha systems:

On Alpha Systems

size-in-blocks(SYS$SYSTEM:SYS$ERRLOG.DMP)
= number-of-error-log-buffers * blocks-per-buffer
+ 2

On VAX Systems

* maximum-number-of-processes

* maximum-number-of-processes

Sufficient page file space is critical to system performance. The AUTOGEN command procedure calculates an appropriate size for your page file space. The size calculated by AUTOGEN should be sufficient. However, to manually calculate the size for page file space, use one of the following formulas.

On VAX Systems

size-in-blocks (total for all page files on the system)
= size-of-average-process (in pages)
* maximum-number-of-processes

If the result of the formula is less than VIRTUALPAGECNT, use the value of VIRTUALPAGECNT instead.

$ WRITE SYS$OUTPUT F$GETSYI ("VIRTUALPAGECNT")

On Alpha Systems

size-in-blocks (total for all page files on the system)
= size-of-average-process (in pages)
* blocks-per-page
* maximum-number-of-processes

For systems over 512MB, follow the steps described below for monitoring page file usage (Section 2.4.3.2), and make adjustments as necessary.

$ @SYS$UPDATE:AUTOGEN SAVPARAMS TESTFILES FEEDBACK

The following lists show the order in which information is written to selective dumps on VAX and Alpha systems.

Note that on Alpha systems, processes are dumped in two stages: the page tables for the process first, and then the body of the process.

Usage Notes on VAX and Alpha Systems

On both VAX and Alpha platforms, no process is dumped twice. For example, on Alpha systems, if the current process is the Swapper, it is dumped only once.

Similarly, on Alpha systems, no global page is dumped twice. Therefore, if a page in the working set of a key process is dumped in the "Key global pages" section, it is not dumped again later just because it is also in the working set of a non-key process.

On Alpha systems, a set of processes, known as key processes, are dumped immediately following PT, S0/S1, and S2, including transition pages that link back to the process. The system manager can designate additional processes to be treated as key processes. These processes have priority over other processes in a dump, thus ensuring that the selected processes are successfully written when the dump file is too small to contain all processes.

How to Perform This Task

You can edit the data file and run the image at any time the system is running. Therefore, if a process is hung, the system manager can designate the process as a priority process and then force a crash.

If there is more than one path to the system disk, the console environment variable DUMP_DEV must describe all paths to the system disk. This ensures that if the original boot path becomes unavailable because of failover, the system can still locate the system disk and write the system dump to it.

If the system disk shadow set has multiple members, the console environment variable DUMP_DEV must describe all paths to all members of the shadow set. This ensures that if the master member changes, the system can still locate the master member and write the system dump to it.

If you do not define DUMP_DEV, the system can write a system dump only to the physical disk used at boot time using only the same physical path used at boot time. For instructions on setting DUMP_DEV, see Section 2.7.1.

Certain configurations (for example, those using Fibre Channel disks) may contain more combinations of paths to the system disk than can be listed in DUMP_DEV. In that case, VSI recommends that you include in DUMP_DEV all paths to what is usually the master member of the shadow set, because shadow set membership changes occur less often than path changes.

You can write the system dump to an alternate disk (see Section 2.7.1), but when doing so you must still define a path to the system disk for writing error logs. Therefore, DUMP_DEV should contain all paths to the system disk in addition to the paths to the alternate dump disk.

If there are more paths than DUMP_DEV can contain, VSI recommends that you define all paths to the dump disk and as many paths as possible (but at least one) to the system disk. Note that the system disk paths must come last in the list.

To ensure that the system can locate the system disk and write the system dump to it when there is more than one path to the system disk, or when the system disk shadow set has multiple members, you must follow the platform-specific instructions regarding booting. On some VAX systems, you must set appropriate register values; on other VAX systems, you must set specific environment variables. See the upgrade and installation supplement for your VAX system for details.

Note that if the system has multiple CI star couplers, the shadow set members must all be connected through the same star coupler.

Designating the Dump Device on Alpha Systems

Designating the Dump Device on I64 Systems

You can designate the dump device on I64 systems by using either of the following:

Using the Boot Manager Utility BOOT_OPTIONS.COM

To designate the dump device with the DUMP_DEV environment variable from the OpenVMS DCL prompt, follow these steps:

Using the EFI Utilities for OpenVMS VMS_SET Command

You can use the EFI utilities for OpenVMS (I64 only) to specify the dump device environment variable DUMP_DEV at the EFI console prompt:

Enabling DOSD on Alpha and I64 Systems

Finally, enable the DOSD bit of the DUMPSTYLE system parameter by setting bit 2. For example, enter the value of 4 at the SYSBOOT> prompt to designate an uncompressed physical dump to an alternate disk with minimal console output:

SYSBOOT> SET DUMPSTYLE 4

SDA CLUE (Crash Log Utility Extractor) commands automate the analysis of crash dumps and maintain a history of all fatal bugchecks on a standalone system or cluster. You can use SDA CLUE commands in conjunction with SDA to collect and decode additional dump file information not readily accessible through standard SDA. You can also use SDA CLUE with Dump Off System Disk (DOSD) to analyze a system dump file that resides on a disk other than the system disk.

SDA> CLUE CONFIG

$ mount/system/noassist $3$dua25: dmp$dev dmp$dev
$ define/system clue$dosd_device dmp$dev

The crash history file, which is created and updated by CLUE, contains key parameters from crash dump files. Unlike crash dumps, which are overwritten with each system failure and are therefore typically available only for the most recent failure, the crash history file is a permanent record of system failures.

After a system fails and physical memory is copied to the crash dump file, CLUE automatically appends the relevant parameters to the file CLUE$OUTPUT:CLUE$HISTORY.DATA when the system is restarted. The remainder of this section describes how you can use CLUE to display the data it has collected; reference information about CLUE is available in the VSI OpenVMS System Management Utilities Reference Manual.

$ DEFINE /SYSTEM CLUE$EXCLUDE_OPERS TRUE

To display data using CLUE, you must first define the following symbol:

$ CLUE :== $CLUE 

After defining the symbol, you can use CLUE to display information by entering the following command:

$ CLUE/DISPLAY
CLUE_DISPLAY>

At the CLUE_DISPLAY> prompt, you can issue commands to perform the following actions:

For more information about CLUE commands, refer to the VSI OpenVMS System Management Utilities Reference Manual.

This section contains instructions for freeing dump information from the page file on VAX and Alpha systems.

How to Perform This Task on VAX Systems

Alternatively, to free the pages in the page file that are taken up by the dump without having to copy the dump elsewhere, enter the ANALYZE/CRASH_DUMP/RELEASE command. This command immediately releases the pages to be used for system paging, effectively deleting the dump. Note that this command does not allow you to analyze the dump before deleting it.

Example

$ ANALYZE/CRASH_DUMP SYS$SYSTEM:PAGEFILE.SYS
  COPY DISK$USER5:[DUMPS]SAVEDUMP.DMP
  EXIT
$ SET FILE/NOBACKUP SYS$SYSTEM:SAVEDUMP.DMP

How to Perform This Task on Alpha Systems

On Alpha systems, as described in the VSI OpenVMS Alpha System Analysis Tools Manual, SDA is automatically invoked by default when the system is rebooted after a system failure.

If the logical CLUE$INHIBIT has been defined, and SDA has not been automatically invoked during system startup, the pages in the page file that are taken up by the dump can be released using the ANALYZE/CRASH_DUMP/RELEASE command. This command immediately releases the pages to be used for system paging, effectively deleting the dump. Note that this command does not allow you to analyze the dump before deleting it.

For a discussion of logical names used by CLUE, refer to VSI OpenVMS Alpha System Analysis Tools Manual.

Because a system dump file can contain privileged information, protect copies of dump files from world read access.

To prevent the system from backing up the complete contents of the file, assign the NOBACKUP attribute to the file with the DCL command SET FILE/NOBACKUP.

Example

$ RUN SYS$SYSTEM:SYSGEN
SYSGEN> INSTALL DUA2:[PAGE_SWAP]PAGEFILE_1.SYS/PAGEFILE
SYSGEN> INSTALL DUA2:[PAGE_SWAP]SWAPFILE_1.SYS/SWAPFILE

Page and swap files other than SYS$SYSTEM:PAGEFILE.SYS and SYS$SYSTEM:SWAPFILE.SYS must be reinstalled each time the system boots. You can do this by adding the commands to install the files to the startup command procedure SYS$MANAGER:SYPAGSWPFILES.COM. The template file SYS$MANAGER:SYPAGSWPFILES.TEMPLATE includes comments that help explain how this file is used.

Before performing this task, you must have created the secondary files, as explained in Section 2.15.

For more information about SYPAGSWPFILES.COM, see VSI OpenVMS System Manager's Manual, Volume 1: Essentials.

You can also use SATELLITE_PAGE.COM to install page and swap files on an OpenVMS Cluster satellite node's local disk. SATELLITE_PAGE.COM is created when you run CLUSTER_CONFIG.COM. For more information about installing page and swap files on a satellite node's local disk, refer to the VSI OpenVMS Cluster Systems Manual manual.

How to Perform This Task

Example

$ EDIT SYS$MANAGER:SYPAGSWPFILES.COM
  [add the following commands to SYPAGSWPFILES.COM:]
   .
   .
   .

$ MOUNT/SYSTEM/NOASSIST DUA2: DISK_SYS2
$ RUN SYS$SYSTEM:SYSGEN
  INSTALL DUA2:[SYSTEM]PAGEFILE_1.SYS /PAGEFILE
  INSTALL DUA2:[SYSTEM]SWAPFILE_1.SYS /SWAPFILE
  EXIT

You can direct AUTOGEN to create new system page, swap, and dump files by adding symbols to MODPARAMS.DAT to specify the name, location, and size of new files to be created and then running AUTOGEN. Before performing this task, you should understand AUTOGEN and its parameter file MODPARAMS.DAT. For more information about when to use AUTOGEN, see Section 1.4. See Section 1.4.4 for information about MODPARAMS.DAT.

AUTOGEN automatically calculates appropriate sizes for system page, swap, and dump files. It also modifies the files to the appropriate sizes and installs them. You can control sizes calculated by AUTOGEN by defining symbols in the file MODPARAMS.DAT. For more information, see Section 2.15.1.2.

How to Perform This Task

PAGEFILE =   0
SWAPFILE =   0
DUMPFILE =   0
ERRLOGDUMP = 0 ! Alpha only

VSI recommends that you use AUTOGEN to change sizes of system page, swap, and dump files. However, you can use the command procedure SYS$UPDATE:SWAPFILES.COM to change the size of primary system page, swap, and dump files. SWAPFILES.COM shows you the current size of the system page, swap, and dump files before you change the sizes.

If you change the sizes of system page, swap, or dump files, you must edit MODPARAMS.DAT to specify the new sizes, as explained in Section 2.15.1.2. If you do not specify the new sizes in MODPARAMS.DAT, AUTOGEN resizes the files next time it runs.

The procedure displays the sizes of the current system page, swap, and dump files in SYS$SYSTEM, and the amount of space remaining on the system disk. It then allows you to enter new sizes, or keep the existing sizes for these files. If you specify a size that is larger than that of an existing file, the procedure automatically extends the size of a page or dump file. If you specify a smaller size for a system page, swap, or dump file, a new version of the file is created.

How to Perform This Task

Example

$ @SYS$UPDATE:SWAPFILES.COM
To leave a file size at its current value type a
carriage return in response to its size prompt.
Current file sizes are:

Directory SYS$SYSROOT:[SYSEXE]

PAGEFILE.SYS;1    100000
SYSDUMP.DMP;1      28000
SWAPFILE.SYS;1     33000

Total of 3 files, 161000 blocks.

There are 128741 available blocks on SYS$SYSDEVICE.

Enter new size for page file: [Return]
Enter new size for system dump file: 30000
%SYSGEN-I-EXTENDED, SYS$SYSROOT:[SYSEXE]SYSDUMP.DMP;1 extended
Enter new size for swap file: [Return]


***********************************************************************
*  Please reboot in order for the new files to be used by the system. *
*  After rebooting, purge obsolete copies of the files.               *
*  DO NOT delete the old files until after the reboot.                *
***********************************************************************

How to Perform This Task

Example

$ RUN SYS$SYSTEM:SYSGEN
SYSGEN> CREATE PAGEFILE.SYS/SIZE=100000
%SYSGEN-I-EXTENDED, SYS$SYSROOT:[SYSEXE]PAGEFILE.SYS;1 extended
SYSGEN> CREATE SWAPFILE.SYS/SIZE=30000
%SYSGEN-I-EXTENDED, SYS$SYSROOT:[SYSEXE]SWAPFILE.SYS;1 extended
SYSGEN> CREATE SYSDUMP.DMP/SIZE=33000
%SYSGEN-I-EXTENDED, SYS$SYSROOT:[SYSEXE]SYSDUMP.DMP;1 extended
SYSGEN> EXIT

Holders of CMKRNL or CMEXEC can write complete process dumps. Holders of any of the other privileges mentioned above can read a process dump wherever it has been written.

In general, nonprivileged users should not be able to read complete process dumps, and by default they cannot do so. However, certain situations require that a nonprivileged user be able to read a complete process dump. Other situations require that a nonprivileged user be able to create a complete process dump but be able to read only a partial process dump.

Rights identifier IMGDMP$READALL enables a nonprivileged user to read a complete process dump. Rights identifier IMGDMP$PROTECT protects a complete process dump from being read by the nonprivileged user that created the process dump. These rights identifiers are created during the installation of OpenVMS by the image SYS$SYSTEM:IMGDMP_RIGHTS.EXE, which is also run automatically during system startup to ensure that these rights identifiers exist with the correct values and attributes.

$ RUN SYS$SYSTEM:IMGDMP_RIGHTS
%PROCDUMP-I-CREATED, rights identifier IMGDMP$READALL successfully created
%PROCDUMP-I-CREATED, rights identifier IMGDMP$PROTECT successfully created

Note that IMGDMP$READALL has no attributes, but IMGDMP$PROTECT is created with the RESOURCE attribute.

$ DEFINE /USER SYSUAF SYS$SYSTEM:SYSUAF.DAT  !if necessary
$ RUN SYS$SYSTEM:AUTHORIZE
UAF> GRANT /IDENTIFIER IMGDMP$READALL <user>
UAF> EXIT

Note that the user must log out and log in again to be able to exercise the rights identifier. A nonprivileged user with rights identifier IMGDMP$READALL can read and write complete process dumps without restriction.

You can choose to set up additional ACLs on the protected directory to further control which users are allowed to read and write process dumps there.

Note that to take a process dump when the image is installed with elevated privileges or belongs to a protected subsystem, the user must hold CMKRNL privilege, and is by definition a privileged user (see Section 2.16.1).

$ SHOW DEVICE SYS$SYSDEVICE

The amount of space required to expand all the libraries that ship in data-reduced format differs, depending on your operating system and configuration. For Alpha systems, you need approximately 60,000 free disk blocks; VAX systems require less. For specific disk requirements, refer to the Upgrade and Installation Manual for your operating system.

If you have less free disk space than is required, or if you do not want to expand all the system libraries, you can choose to expand only some of them. For example, you might expand only the system help library (HELPLIB.HLB) and other libraries that are used frequently on your system, and leave the rest in data-reduced format.

The Library Decompression utility is a command procedure, LIBDECOMP.COM, located in the SYS$UPDATE directory. LIBDECOMP.COM uses LIBRARY commands to expand (decompress) or reduce (compress) any or all of the system libraries that ship in data-reduced format. (For a list of these libraries, see Section 3.9.2.1.)

The LIBDECOMP.COM command procedure allows you to enter one command instead of multiple LIBRARY commands to expand or reduce all or many libraries in one operation. LIBDECOMP.COM can be executed interactively (see Section 3.9.2.2) or in batch mode (see Section 3.9.2.3).

@SYS$UPDATE:LIBDECOMP [parameters]

$ @SYS$UPDATE:LIBDECOMP HELP

$ @SYS$UPDATE:LIBDECOMP LIST

 $ @SYS$UPDATE:LIBDECOMP LIST
                   OpenVMS Library Decompression Utility
                 List of all libraries known to LIBDECOMP
       "Library not present" indicates not installed on this system
 Libraries in SYS$SYSROOT:
       Library                     Size
   1) [SYSHLP]ACLEDT.HLB            70   Reduced format
   2) [SYSHLP]BKM$HELP.HLB         156   Reduced format
   3) [SYSHLP]DBG$HELP.HLB        1234   Reduced format
   4) [SYSHLP]DBG$UIHELP.HLB       269   Reduced format
   5) [SYSHLP]EDTHELP.HLB          154   Reduced format
   6) [SYSHLP]EVE$HELP.HLB         676   Reduced format
   7) [SYSHLP]EVE$KEYHELP.HLB       99   Reduced format
   8) [SYSHLP]EXCHNGHLP.HLB         83   Reduced format
   9) [SYSHLP]HELPLIB.HLB         9179   Reduced format
  10) [SYSHLP]LANCP$HELP.HLB       119   Reduced format
  11) [SYSHLP]LATCP$HELP.HLB       157   Reduced format
  12) [SYSHLP]MAILHELP.HLB         211   Reduced format
  13) [SYSHLP]NCPHELP.HLB          261   Reduced format
  14) [SYSHLP]SDA.HLB              308   Reduced format
  15) [SYSHLP]SHWCLHELP.HLB        103   Reduced format
  16) [SYSHLP]SYSGEN.HLB           337   Reduced format
  17) [SYSHLP]SYSMANHELP.HLB       492   Reduced format
  18) [SYSHLP]TPUHELP.HLB          575   Reduced format
  19) [SYSHLP]UAFHELP.HLB          241   Reduced format
  20) [SYSLIB]LANIDEF.MLB          181   Reduced format
  21) [SYSLIB]LIB.MLB             2715   Reduced format
  22) [SYSLIB]STARLET.MLB         2335   Reduced format
  23) [SYSLIB]SYSBLDMLB.MLB                            Library not present
  24) [SYSLIB]DECCRTL.OLB                              Library not present
  25) [SYSLIB]STARLET.OLB        27461   Reduced format
  26) [SYSLIB]SYSBLDLIB.OLB                            Library not present
  27) [SYSLIB]VAXCRTL.OLB         1163   Reduced format
  28) [SYSLIB]VAXCRTLD.OLB        1587   Reduced format
  29) [SYSLIB]VAXCRTLDX.OLB       1506   Reduced format
  30) [SYSLIB]VAXCRTLT.OLB        1434   Reduced format
  31) [SYSLIB]VAXCRTLTX.OLB       1449   Reduced format
  32) [SYSLIB]VAXCRTLX.OLB        1285   Reduced format
  33) [SYSLIB]ERFLIB.TLB            64   Reduced format
  34) [SYSLIB]LIB_ADA_SUBSET.TLB  1839   Reduced format
  35) [SYSLIB]NTA.TLB               34   Reduced format
  36) [SYSLIB]STARLETSD.TLB       3940   Reduced format
  37) [SYSLIB]SYS$LIB_C.TLB       9442   Reduced format
  38) [SYSLIB]SYS$STARLET_C.TLB   5864   Reduced format
  39) [SYSLIB]VMS$VOLATILE_PRIVATE_INTERFACES.OLB   445   Reduced format
  40) [SYSLIB]STARLET_RECENT_ADA_SUBSET.TLB   1100   Reduced format
  Total Libraries:  37           78568

               OpenVMS Library Decompression Utility
                 Candidate Libraries to be expanded
 (Libraries not present and libraries already expanded are not listed)
   1  ACLEDT.HLB           13  NCPHELP.HLB          25  VAXCRTLD.OLB
   2  BKM$HELP.HLB         14  SDA.HLB              26  VAXCRTLDX.OLB
   3  DBG$HELP.HLB         15  SHWCLHELP.HLB        27  VAXCRTLT.OLB
   4  DBG$UIHELP.HLB       16  SYSGEN.HLB           28  VAXCRTLTX.OLB
   5  EDTHELP.HLB          17  SYSMANHELP.HLB       29  VAXCRTLX.OLB
   6  EVE$HELP.HLB         18  TPUHELP.HLB          30  ERFLIB.TLB
   7  EVE$KEYHELP.HLB      19  UAFHELP.HLB          31  LIB_ADA_SUBSET.TLB
   8  EXCHNGHLP.HLB        20  LANIDEF.MLB          32  NTA.TLB
   9  HELPLIB.HLB          21  LIB.MLB              33  STARLETSD.TLB
  10  LANCP$HELP.HLB       22  STARLET.MLB          34  SYS$LIB_C.TLB
  11  LATCP$HELP.HLB       23  STARLET.OLB          35  SYS$STARLET_C.TLB
  12  MAILHELP.HLB         24  VAXCRTL.OLB
       36  VMS$VOLATILE_PRIVATE_INTERFACES.OLB
       37  STARLET_RECENT_ADA_SUBSET.TLB

           A  ALL libraries to be expanded
           H  Display HELP information for LIBDECOMP
           E  EXIT this procedure

"ALL" specified; all libraries will be processed

* Enter a letter or the number(s) of libraries to be expanded
  (Separate multiple numbers with a comma)

SUBMIT SYS$UPDATE:LIBDECOMP /PARAMETERS=(p1[,p2,...])

An alternative to using the Library Decompression utility to expand or reduce an individual library is to use the DCL command LIBRARY with the /DATA qualifier. With this method, you can specify only one library per LIBRARY command.

LIBRARY library-name.ext /DATA=EXPAND

LIBRARY library-name.ext /DATA=REDUCE

You must always specify the library extension (.HLB, .MLB, .OLB, or .TLB).

$ LIBRARY [SYSHLP]HELPLIB.HLB /DATA=EXPAND

For information about other qualifiers for the LIBRARY command, see online help for LIBRARY or refer to the VSI OpenVMS Command Definition, Librarian, and Message Utilities Manual.

An image is a collection of procedures and data bound together by the Linker utility. Executable images can be executed (or run) in a process, either by a command line interpreter (CLI) or the $CREPRC system service. Usually, executable programs have the file type .EXE.

There are three types of images:

When you install an image with INSTALL, the image is assigned attributes and becomes known to the system. For this reason, an installed image is also called a known image.

The image activator processes search lists in two passes, in order to favor known images. On its first pass through the search list, the image activator looks up images as known files. If needed, on a second pass through the search list, the image activator looks up images on disk.

The system defines known images in internal data structures called known file entries. Each entry identifies the file name of the installed image and the attributes with which it was installed (for information about attributes of installed images, see Section 3.10.3).

Known file entries last only while the system is operating. If the system is shut down or fails for any reason, you must reinstall all known images after the system is rebooted.

By specifying appropriate qualifiers to INSTALL commands, you can assign attributes to known images. Table 3.2 describes these attributes and the qualifiers that are used to assign them to known images.

You can install images for the following reasons:

Because an installed file requires system resources, such as paged dynamic memory, install those files that most improve system performance and site requirements. The INSTALL command LIST provides information about installed images to help you evaluate the merits of installing images. For example, the LIST command calculates the number of times each image is accessed, and shows the number of concurrent accesses, so you can determine if the installation of the images is worth the overhead.

You can improve image activation performance by installing images that run frequently. Image activation performance improves when programs are installed because the operating system opens installed files by file ID rather than by file name, thus eliminating costly directory operations.

Installing images as header resident further enhances activation performance because the system avoids the overhead of I/O operations to read the image header into memory.

To install an image as header resident, specify the /HEADER_RESIDENT qualifier when you install the image. This makes the header of the image file remain permanently resident, saving disk I/O. Specifying the /HEADER_RESIDENT qualifier implicitly makes the images permanently open.

Image headers are stored in paged dynamic memory. The size of the image headers varies.

Frequently accessed images, critical to a site's operations, can be installed as open images. To install an image as permanently open, specify the /OPEN qualifier when you install the image. The image file remains open, so access to the image does not require a call to the file system. The cost of keeping an image file permanently open is approximately 512 bytes of nonpaged dynamic memory per file.

Using shared address data on OpenVMS Alpha systems improves performance at the following times:

For details, refer to the VSI OpenVMS System Management Utilities Reference Manual.

Related Terms

Explanations of terms related to shared address data follow.

You can conserve physical memory by installing images that usually run concurrently from several processes. When an image is not installed, or is installed without the shared attribute, each process running the image requires private sections in memory. Shared images conserve physical memory because only one copy of the code needs to be in memory at any time, and many users can access the code concurrently. Use the /SHARED qualifier to install images as shared images.

When you install an image with the shared attribute, permanent system global sections are created. Execution of non-copy-on-reference global sections requires only one copy per section to be in physical memory, no matter how many processes are running the image to which the sections belong.

The number of images you can install with the shared attribute is restricted by the GBLPAGES and GBLSECTIONS system parameters. For more information about these system parameters, refer to the VSI OpenVMS System Management Utilities Reference Manual.

There are two ways to allow an image to execute in an enhanced privilege environment:

When a process performs one of the following actions, the image activator enters a restricted mode of operation similar to that entered when a privileged program is run:

In this mode of operation:

When you use INSTALL commands, your file specifications must name existing executable or shareable images. OpenVMS RMS resolves each file specification using the following defaults:

You can specify a specific version of the file as the known version of the image with the CREATE or REPLACE command. Even if other versions of the file exist, the version that you specify will be the version that satisfies all known file lookups for the image.

Before performing this task, you should understand the following points:

How to Perform This Task

Use the INSTALL command LIST to display information about known images.

The information displayed with the /FULL qualifier of the LIST command can help you determine if installing an image is worth the expense.

How to Perform This Task

Example

The following example displays complete information about the installed image LOGINOUT.EXE, including the number of accesses, the number of concurrent accesses, and the number of global sections created:

$ INSTALL
INSTALL> LIST/FULL LOGINOUT
DISK$VMS551:<SYS2.SYSCOMMON.SYSEXE>.EXE
   LOGINOUT;2       Open Hdr Shar Prv
        Entry access count         = 36366
        Current / Maximum shared   = 1 / 10
        Global section count       = 3
        Privileges = CMKRNL SYSNAM LOG_IO ALTPRI TMPMBX SYSPRV
INSTALL>

If a shareable image is not located in SYS$SHARE, you must define a logical name for that image in order to run an executable image linked against it. For example, if the file specification for STATSHR is SYS$SHARE:STATSHR.EXE, no logical name is necessary. But if you put STATSHR in SYS$DEVICE:[TEST], you must define STATSHR as a logical name before running an executable image that calls it. The logical name must be the same one that was used as the input file specification for the shareable image when it was linked (this is the same name used in installation). For example:

$ DEFINE STATSHR SYS$SYSDEVICE:[TEST]STATSHR

By redefining the logical name of a shareable image, you can replace that shareable image with another without requiring the calling executable image to relink. For example, the following statement redefines the file name STATSHR. It becomes the logical name of the shareable image SYS$SYSDEVICE:[MAIN]STATSHR.EXE for executable images calling STATSHR.

$ DEFINE STATSHR SYS$SYSDEVICE:[MAIN]STATSHR

The INSTALL command REMOVE removes a known file entry for an image and deletes any global sections created when the image was installed. Note that a volume cannot be dismounted while any known file entries are associated with it. To dismount a volume, you must delete all known images associated with it. You must also wait for all processes using those images to exit. Use the DCL command SHOW DEVICES/FILES to determine the status of the files.

For more information about the INSTALL command DELETE, refer to the VSI OpenVMS System Management Utilities Reference Manual.

OpenVMS provides a mechanism to reserve non-fluid memory for use within a memory-resident global demand-zero section. The reserved memory may either be simply a deduction from the system's nonfluid memory size or pages may be preallocated.

Using the Reserved Memory Registry ensures that AUTOGEN tunes the system properly to not include memory-resident section pages in its calculation of the system's fluid page count. AUTOGEN sizes the system pagefile, number of processes and working set maximum size based on the system's fluid page count. A system can experience severe performance problems if AUTOGEN adjusts parameters based upon a fluid page count that does not account for the physical memory that is permanently reserved for some other purpose.

Using the Reserved Memory Registry also ensures that contiguous, aligned memory is available for memory-resident sections when the allocate option is used.

SYS$SYSTEM:VMS$RESERVED_MEMORY.DATA

SYSMAN RESERVED_MEMORY ADD gs_name -
                       /GROUP = n -
                       /SIZE = {size of reserved memory, unit: MB} -
                       /[NO]ALLOCATE -
                       /[NO]ZERO -
                       /[NO]PAGE_TABLES

You can remove a reserved memory entry by issuing the following SYSMAN command:

SYSMAN RESERVED_MEMORY REMOVE gs_name /GROUP = n

The specified gs_name is the name of the memory-resident section associated with the entry being removed from the Reserved Memory Registry. A name must be specified.

The value n specified by the /GROUP qualifier is the UIC group number (in octal) associated with the memory-resident section being removed. If the memory-resident global section is a group section, you must specify the /GROUP qualifier. If the memory-resident global section is a system global section, you must not specify the /GROUP qualifier.

If page tables are reserved for the named memory-resident global section, the additional reserved memory is also removed.

The REMOVE command only removes entries from the Reserved Memory Registry data file; it does not affect memory within the running system.

SYSMAN> RESERVED_MEMORY FREE gs_name /GROUP = n

The configuration of an OpenVMS Alpha application that uses memory-resident global sections performs the following steps:

If you have an OpenVMS Cluster system that contains earlier versions of OpenVMS Alpha or OpenVMS VAX and you want to use XFC with OpenVMS Version 7.3 or higher, you must install remedial kits on the systems that are running the earlier versions of OpenVMS. See VSI OpenVMS Alpha Version 7.3-2 Release Notes for information on the required kits.

This section describes how to control the minimum and maximum size of XFC.

XFC is held in virtual memory in S2 space and automatically shrinks and grows, depending on your I/O workload and how much spare memory is available on your system. S2 space is a 64-bit address space, so the cache can grow to very large sizes when required.

As your I/O workload increases, the cache automatically grows, but never to more than the maximum size. And when your applications need memory, the cache automatically shrinks, but never to less than the minimum size.

$ SHOW MEMORY /RESERVED
              System Memory Resources on 11-MAY-2016 15:50:25.64

Memory Reservations (pages):    Group    Reserved      In Use       Type
  VCC$MIN_CACHE_SIZE              ---        1536        1536  Allocated
Total (400.00 Mb reserved)                   1536        1536

$ RUN SYS$SYSTEM:SYSGEN
SYSGEN> USE ACTIVE
SYSGEN> SET VCC_MAX_CACHE 40
SYSGEN> WRITE ACTIVE
$ SET CACHE /RESET

$ RUN SYS$SYSTEM:SYSGEN
SYSGEN> USE CURRENT
SYSGEN> SET VCC_MAX_CACHE 40
SYSGEN> WRITE CURRENT

$ RUN SYS$SYSTEM:SYSGEN
SYSGEN> USE CURRENT
SYSGEN> SET VCC_MAX_CACHE 8000
SYSGEN> WRITE ACTIVE
$ RUN SYS$SYSTEM:SYSMAN
SYSMAN> RESERVED_MEMORY ADD VCC$MIN_CACHE_SIZE /SIZE=8000 /ALLOCATE -
_SYSMAN> /NOGLOBAL_SECTION /NOZERO /NOPAGE_TABLE/RAD=0

The dynamic system parameter VCC_MAX_IO_SIZE controls the maximum size of I/O that can be cached by XFC. This parameter specifies the size in blocks. By default, it is 128.

Example

$ RUN SYS$SYSTEM:SYSGEN
SYSGEN> USE ACTIVE
SYSGEN> SET VCC_MAX_IO_SIZE 1000
SYSGEN> WRITE ACTIVE

This series of commands affects I/Os to volumes currently mounted on the local node, as well as to volumes mounted in the future. After you enter these commands, XFC does not cache I/Os that are larger than 1,000 blocks. The SHOW MEMORY /CACHE /FULL command provides a histogram of I/O sizes that can provide guidelines for efficient parameter setting.

To prevent XFC to from caching a particular file, such as a database file, set the caching attribute of the file to no caching.

The caching attribute of a file is the default caching option that is used by XFC when an application accesses the file without specifying which caching option it wants to use. The caching option can be either write-through caching or no caching.

Examples

XFC uses a technique called read-ahead caching to improve the performance of applications that read data sequentially. It detects when a file is being read sequentially in equal-sized I/Os, and fetches data ahead of the current read, so that the next read instruction can be satisfied from cache.

To disable read-ahead caching on the local node, set the dynamic system parameter VCC_READAHEAD to 0. By default, this parameter is 1, which allows the local node to use read-ahead caching.

Example

$ RUN SYS$SYSTEM:SYSGEN
SYSGEN> USE CURRENT
SYSGEN> SET VCC_READAHEAD 0
SYSGEN> WRITE ACTIVE

This series of commands affects volumes currently mounted on the local node, as well as volumes mounted in the future. Once you enter these commands, read-ahead caching is not used on the local node.

XFC provides more information than VIOC. For example, you can obtain information on system-wide, volume-wide, or even a per-file basis. Disk I/O response times are also available. See the VSI OpenVMS DCL Dictionary for a description of the SHOW MEMORY command.

$ SHOW MEMORY /CACHE

              System Memory Resources on 26-JAN-2017 15:58:18.71

Extended File Cache  (Time of last reset: 24-JAN-2017 15:03:39.05)
 Allocated (Mbytes)        3000.00  Maximum size (Mbytes)     5120.00
 Free (Mbytes)             2912.30  Minimum size (Mbytes)     3000.00
 In use (Mbytes)             87.69  Percentage Read I/Os          98%
 Read hit rate                 92%  Write hit rate                 0%
 Read I/O count             178136  Write I/O count              1867
 Read hit count             165470  Write hit count                 0
 Reads bypassing cache        2802  Writes bypassing cache         39
 Files cached open             392  Files cached closed           384
 Vols in Full XFC mode           0  Vols in VIOC Compatible mode    4
 Vols in No Caching mode         1  Vols in Perm. No Caching mode   0