System Parameters

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System parameters are variables that let you control the way your OpenVMS system functions. Your distribution kit provides default values for system parameters to allow you to boot any supported configuration. When your system is installed or upgraded, AUTOGEN executes to evaluate your hardware configuration, estimate typical work loads, and adjust the values of system parameters as needed. Each system parameter has associated minimum and maximum values that define the scope of allowable values.

There are dynamic and static system parameters. Dynamic system parameters can be changed on a running system; static system parameters need a reboot to become effective.

The OpenVMS System Management Utilities Reference Manual lists and describes each system parameter.

There are several ways to look up the value of a parameter on your system:

  • use the SYSGEN utility. You can also use it to modify system parameters.
  • use the F$GETSYI() lexical function (use the name of the specific parameter as the item)


The following categories of system parameters exist:

Category Description
ACP Parameters associated with file system caches and Files-11 ancillary control processes (ACPs)
CLUSTER Parameters that affect OpenVMS Cluster operation
JOB Job control parameters
LGI Login security parameters
PQL Parameters associated with process creation limits and quotas
RMS Parameters associated with OpenVMS Record Management Services (RMS)
SCS Parameters that control System Communications Services (SCS) and port driver operation. The parameters that affect SCS operation have the prefix SCS. The parameters that affect the CI780/CI750 port driver have the prefix PA
SPECIAL Special parameters used by VSI. Change these parameters only if recommended by VSI personnel, or if specifically instructed in the installation guide or release notes of an VSI layered product
SYS Parameters that affect overall system operation
TTY Parameters associated with terminal behavior