HP OpenVMS Systems Documentation

Content starts here
HP OpenVMS Version 8.3 Upgrade and Installation Manual > Chapter 7 After Installing or Upgrading the OpenVMS Operating System

Modifying System Parameters

  Table of Contents



Based on your examination of AGEN$PARAMS.REPORT, you might need to modify parameter values in MODPARAMS.DAT. Read the notes in “General Notes About Modifying System Parameters”. These notes apply both to modifications being made either after a new installation or after an upgrade. If you are modifying system parameters after an upgrade, also see “Modifying System Parameters After an Upgrade”.

General Notes About Modifying System Parameters

When modifying system parameters, note the following:

  • In general, let AUTOGEN calculate system parameters. You can hardcode values (such as GBLPAGES=value), but doing so overrides AUTOGEN and might not allow it to set an optimal value based on observed usage.

  • Whenever possible, use MIN_parameter values (such as MIN_GBLPAGES) to set the minimum value that can be set for a parameter by AUTOGEN. AUTOGEN increases the value if necessary. It also adjusts related parameters unless they are hardcoded, in which case information is provided in the AGEN$PARAMS.REPORT file. Use MAX_parameter values to set a maximum value when it is necessary to limit a parameter to a known maximum value (this is rarely necessary).

  • Enter numeric values as integers without commas (for example, 10000). Enter alphabetic characters in lower or uppercase.

  • HP recommends that you include comments in the MODPARAMS.DAT file indicating who changed the value, when it was done, and why it was done. An exclamation point (!) serves as a comment starter and can appear anywhere on a line. The following example illustrates the modifications recommended in the preceding bulleted items:

       ! the following changes made by K.Newcomb on 9/20/03
    SWAPFILE=0 ! don’t re-size the SWAPFILE on AUTOGEN runs
    MIN_gblsections=750 ! required for DECwindows MOTIF
    MIN_NPAGEDYN=2750000 ! set npagedyn to a min of 2.75 million

For more information about the MODPARAMS.DAT file and about using AUTOGEN in general, see the HP OpenVMS System Manager's Manual, Volume 2: Tuning, Monitoring, and Complex Systems.

Modifying System Parameters After an Upgrade

Review the file SYS$SYSTEM:MODPARAMS.DAT. The upgrade procedure created a new version of this file. The old version is named SYS$SYSTEM:MODPARAMS.DAT_OLD. The new MODPARAMS.DAT file contains all the parameters in the old file, plus various parameters that the upgrade procedure added to ensure that all necessary system parameters are properly propagated from the earlier version of OpenVMS. The upgrade procedure also adds comment lines to explain the source of the parameters in each section of the new MODPARAMS.DAT file.

Note that the old MODPARAMS.DAT is included in the new MODPARAMS.DAT each time an upgrade is performed. Because of this, if MODPARAMS.DAT is not reviewed and cleaned up after each upgrade, it might eventually contain many levels of duplicated parameters. For this reason, you should review MODPARAMS.DAT after each upgrade. This enables you to eliminate any duplication. You can also take this opportunity to modify any parameters, if necessary.

Based on your examination of AGEN$PARAMS.REPORT, you might need to modify parameter values in MODPARAMS.DAT.

The following subsections are examples of instances where you need to modify parameters in MODPARAMS.DAT.

System File Sizes

AUTOGEN sets the following files at sizes appropriate for your system:




If you have special workloads or configurations, you can specify different sizes for these files by performing the following steps:

  1. Log in to the SYSTEM account.

  2. Enter the following command:

  3. If the file sizes displayed need to be adjusted, add symbols to the MODPARAMS.DAT file (described in detail in the HP OpenVMS System Manager's Manual, Volume 2: Tuning, Monitoring, and Complex Systems), and repeat step 2 until you are satisfied with the file sizes.

  4. When you are satisfied with the file sizes, enter the following command to ensure that the modified system files are installed when the system is rebooted:


OpenVMS Cluster Parameters

If you are upgrading an OpenVMS Cluster system, note the following:

  • The upgrade procedure creates a new MODPARAMS.DAT for each system root on your system disk. Normally, there is one root for each computer that boots from the system disk. You must review and adjust each of these MODPARAMS.DAT files individually.

    The MODPARAMS.DAT file for the system on which you are running is located in the SYS$SYSTEM:MODPARAMS.DAT file. The MODPARAMS.DAT files for other roots on the same system disk can be found in SYS$SYSDEVICE:[SYSx.SYSEXE]MODPARAMS.DAT, where x represents the root number; for example, SYS0, SYS1, SYS2, and so forth. (Valid root numbers might include hexadecimal digits -- SYSA, SYSB, and so forth.)

  • Be sure the EXPECTED_VOTES value is correct. This value is the sum of all votes in the cluster. For example, if there are five computers in the cluster and each has one vote, the value is 5.