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HP OpenVMS System Manager's Manual, Volume 2:... |
Managing System Parameters |
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Understanding System Parameters
The HP OpenVMS System Management Utilities Reference Manual lists and describes each system parameter.
Your distribution kit provides default values for system parameters to allow you to boot any supported configuration. When your system is installed or upgraded, the SYS$UPDATE:AUTOGEN.COM command procedure 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.
Parameter Types
System parameters can be one or more of the following types:
| Type | Description |
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Dynamic
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The value of a dynamic system
parameter can be modified while the system is active by changing
the active value in memory. In contrast, if
you change the value of a parameter that is not dynamic, you must
change the current value stored in the parameter
file, and you must reboot the system for the changed value to take
effect. For information about active and current values, see
Default, Current, and Active Values.
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General
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The value of a general parameter
affects the creation and initialization of data structures at boot
time.
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Major
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Major parameters are most
likely to require modification.
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Special
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Special parameters are intended for use
only by HP. Change these parameters only if recommended by HP personnel
or in the installation guide or release notes of a HP-supplied layered
product.
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Parameter Categories by Function
System parameters can be divided into the following categories, according to their function:
| Category | Function |
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ACP |
Parameters associated with the file system
caches and Files-11 XQP (extended QIO procedure) or ancillary control
processes (ACPs).1
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Cluster |
Parameters that affect VAXcluster or OpenVMS
Cluster system operation. |
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Job |
Parameters that control jobs. |
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LGI |
Parameters that affect login security. |
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Multiprocessing |
Parameters associated with symmetric multiprocessing. |
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PQL
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Parameters associated with process creation
limits and quotas. |
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RMS |
Parameters associated with OpenVMS Record Management
Services (RMS). |
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SCS |
Parameters that control system communication
services (SCS) and port driver operation. The parameters that affect
SCS operation have the prefix SCS. |
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SYS |
Parameters that affect overall system operation. |
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TTY |
Parameters associated with terminal behavior. |
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User-defined |
The following parameters can be user-defined: USERID1 (dynamic) USERID2 (dynamic) USER3 USER4 |
Default, Current, and Active Values
A system has several different sets of values for system parameters.
The following table describes these values:
| Value | Description |
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Default
values
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Values provided with the
system to allow you to boot any supported configuration.
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Current
values
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Values stored in the default
parameter file on disk and used to boot the system.
On VAX systems, the default parameter file is VAXVMSSYS.PAR. On Alpha systems, the default parameter file is ALPHAVMSSYS.PAR. |
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Active
values
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Values that are stored in
memory and are used while the system is running. You can change
the active value on a running system only for system parameters
categorized as dynamic system parameters.
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Values stored in other parameter files
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For special purposes, you can create
a parameter file other than the default parameter file that is used
to store current values.
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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 Managing System Parameters with SYSMAN. For more information about managing parameters with SYSGEN, see Managing System Parameters with SYSGEN.
Pages and Pagelets
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), 16KB, 32KB, or 64KB. A pagelet 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 8KB, 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. Showing Parameter Values with SYSMAN and Showing Parameter Values with SYSGEN explain how to show parameter values and their units of allocation.
1 Many ACP parameters are applicable only when Files-11 On-Disk Structure Level 1 disks are mounted or when an ACP is specifically requested during a mount command. In versions of the operating system before VAX VMS Version 4.0, a separate process, the ancillary control process (ACP), performed file operations such as file opens, closes, and window turns. VAX VMS Version 4.0 introduced the XQP (extended QIO procedure), which allows every process on the system to perform these operations. For compatibility reasons, the names of the parameters have not changed.
( Number takes you back )
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