HP OpenVMS System Management Utilities Reference Manual


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This cell is used for enabling and disabling VBS dynamic capabilities that are valid only when VBS is enabled. The following table indicates the result for each value:
Bit Result
0 Enables VBS to perform first-level data reduction when switching processes. The default is enabled.
1 Enables VBS to perform second-level data reduction when switching processes. The default is enabled.
2 Requests VBS to perform an optimization that detects empty private page table pages on the modified list and frees them directly to the free list versus writing them to the page file. The default setting is enabled.
3-7 Reserved to HP for future use.

VCC_FLAGS (A)

(Alpha only) The static system parameter VCC_FLAGS enables and disables file system data caching. If caching is enabled, VCC_FLAGS controls which file system data cache is loaded during system startup.
Value Description
0 Disables file system data caching on the local node and throughout the OpenVMS Cluster.

In an OpenVMS Cluster, if caching is disabled on any node, none of the other nodes can use the extended file cache or the virtual I/O cache. They can't cache any file data until that node either leaves the cluster or reboots with VCC_FLAGS set to a nonzero value.

1 Enables file system data caching and selects the Virtual I/O Cache. This is the default for VAX systems.
2 Enables file system data caching and selects the extended file cache. This is the default for Alpha systems.

Note

On I64 systems, the volume caching product ([SYS$LDR]SYS$VCC.EXE) is not available. XFC caching is the default caching mechanism. Setting the VCC_FLAGS parameter to 1 is equivalent to not loading caching at all or to setting VCC_FLAGS to 0.

VCC_MAXSIZE (A)

(Alpha and I64) The static system parameter VCC_MAXSIZE controls the size of the virtual I/O cache. VCC_MAXSIZE, which specifies the size in blocks, is 3,700,000 by default.

The virtual I/O cache cannot shrink or grow. Its size is fixed at system startup.

To adjust the XFC size, use the VCC_MAX_CACHE system parameter.

VCC_MAX_CACHE (D)

(Alpha and I64) The dynamic system parameter VCC_MAX_CACHE controls the maximum size of the extended file cache. It specifies the size in megabytes. By default, VCC_MAX_CACHE has a special value of --1 for people who do not want to tune their systems manually; this value means that at system startup, the maximum size of the extended file cache is set to 50 percent of the physical memory on the system.

The extended file cache can automatically shrink and grow, depending on your I/O workload and how much spare memory your system has. As your I/O workload increases, the cache automatically grows, but never to more than the maximum size. When your application needs memory, the cache automatically shrinks.

The value of VCC_MAX_CACHE at system startup sets an upper limit for the maximum size of the extended file cache. You cannot increase the maximum size of VCC_MAX_CACHE beyond its value at boot time. For example, if VCC_MAX_CACHE is 60 MB at system startup, you can then set VCC_MAX_CACHE to 40, which decreases the maximum size to 40 MB. If you then set VCC_MAX_CACHE to 80, the maximum size is only increased to 60 MB, the value set at system startup.

Note that VCC_MAX_CACHE is a semi-dynamic parameter. If you change its value, you must enter the DCL command SET CACHE/RESET for any changes to take effect immediately. Otherwise, it might take much more time for the changes to take effect.

If you are using the reserved memory registry to allocate memory permanently, you must set the VCC$MIN_CACHE_SIZE entry in the reserved memory registry to a value less than or equal to VCC_MAX_CACHE at system startup time.

For instructions on setting permanent memory allocations for the cache, see the HP OpenVMS System Manager's Manual.

VCC_MAX_IO_SIZE (D)

(Alpha and I64) The dynamic system parameter VCC_MAX_IO_SIZE controls the maximum size of I/O that can be cached by the extended file cache. It specifies the size in blocks. By default, the size is 127 blocks.

Changing the value of VCC_MAX_IO_SIZE affects reads and writes to volumes currently mounted on the local node, as well as reads and writes to volumes mounted in the future.

If VCC_MAX_IO_SIZE is 0, the extended file cache on the local node cannot cache any reads or writes. However, the system is not prevented from reserving memory for the extended file cache during startup if a VCC$MIN_CACHE_SIZE entry is in the reserved memory registry.

VCC_MAX_LOCKS

(Alpha and I64) VCC_MAX_LOCKS is a special parameter reserved for HP use only. Extended file cache will use this parameter in future versions.

VCC_MINSIZE

(VAX only) VCC_MINSIZE sets the lower limit in pages of memory used by virtual I/O cache.

This special parameter is used by HP and is subject to change. Do not change this parameter unless HP recommends that you do so.

VCC_PAGESIZE

(Alpha and I64) VCC_PAGESIZE is a special parameter reserved for HP use only. Extended file cache will use this parameter in future versions.

VCC_PTES

(VAX only) The static system parameter VCC_PTES controls the maximum size of the virtual I/O cache. It specifies the potential size in pages.

The virtual I/O cache automatically shrinks and grows, depending on your I/O workload and how much spare memory your system has. As your I/O workload increases, the cache automatically grows, but never to more than the maximum size. When your applications need memory, the cache automatically shrinks.

This special parameter is used by HP and is subject to change. Do not change this parameter unless HP recommends that you do so.

VCC_READAHEAD (D)

(Alpha and I64) The dynamic system parameter VCC_READAHEAD controls whether the extended file cache can use read-ahead caching. Read-ahead caching is a technique that improves the performance of applications that read data sequentially.

By default VCC_READAHEAD is 1, which means that the extended file cache can use read-ahead caching. The extended file cache 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 stop the extended file cache from using read-ahead caching, set VCC_READAHEAD to 0.

Changing the value of VCC_READAHEAD affects volumes currently mounted on the local node, as well as volumes mounted in the future.

Readahead I/Os are totally asynchronous from user I/Os and only take place if sufficient system resources are available.

VCC_RSVD

(Alpha and I64) VCC_RSVD is a special parameter reserved for HP use only. Extended file cache will use this parameter in future versions.

VCC_WRITEBEHIND

(Alpha and I64) VCC_WRITEBEHIND is reserved for HP use only. Extended file cache will use this parameter in future versions.

VCC_WRITE_DELAY

(Alpha and I64) VCC_WRITE_DELAY is reserved for HP use only.

VHPT_SIZE

(I64 only) VHPT_SIZE is the number of kilobytes to allocate for the virtual hash page table (VHPT) on each CPU in the system:

If a VHPT is created, the smallest size is 32KB. The VHPT_SIZE must be a power of 2 KB in size. If the number specified is not a power of 2, OpenVMS chooses a VHPT size to use for your system that is close to the number specified.

If insufficient memory is available during system startup, OpenVMS might choose a smaller size for the VHPT of each CPU.

A summary of possible values for VHPT_SIZE is in the following table:
Value Description
0 Do not create a VHPT on each CPU.
1 (default) OpenVMS chooses a VHPT of an appropriate size for each CPU.
n Create a VHPT of nKB for each CPU, where n is a power of 2 that is 32 or greater. (The maximum value, however, is platform-dependent.)

VIRTUALPAGECNT (A,G,M)

On VAX systems, VIRTUALPAGECNT sets the maximum number of virtual pages that can be mapped for any one process. A program is allowed to divide its virtual space between the P0 and P1 tables in any proportion.

If you use SYS$UPDATE:LIBDECOMP.COM to decompress libraries and the VIRTUALPAGECNT setting is low, make sure you set the PGFLQUOTA field in the user authorization file to at least twice the size of the library.

At installation time, AUTOGEN automatically sets an appropriate value for VIRTUALPAGECNT. The value depends on the particular configuration---the type and number of graphics adapters on the system, if any exist. You cannot set VIRTUALPAGECNT below the minimum value required for your graphics configuration.

Because the VIRTUALPAGECNT setting supports hardware address space rather than system memory, do not use the value of VIRTUALPAGECNT that AUTOGEN sets to gauge the size of your page file.

Starting with OpenVMS Version 7.0, VIRTUALPAGECNT has been an obsolete parameter on Alpha systems. Note, however, that the parameter remains in existence on Alpha and I64 systems for compatibility purposes and has a default and maximum value of %X7FFFFFFF. SYSBOOT and AUTOGEN enforce this default value.

VMS*

VMSD1, VMSD2, VMSD3, VMSD4, VMS5, VMS6, VMS7, and VMS8 are special parameters reserved for HP use. VMSD1 through VMSD4 are DYNAMIC.

VOTES (A)

VOTES establishes the number of votes an OpenVMS Cluster member system contributes to a quorum.

WBM_MSG_INT (D)

WBM_MSG_INT is one of three system parameters that are available for managing the update traffic between a master write bitmap and its corresponding local write bitmaps in an OpenVMS Cluster system. The others are WBM_MSG_UPPER and WBM_MSG_LOWER. These parameters set the interval at which the frequency of sending messages is tested and also set an upper and lower threshold that determine whether the messages are grouped into one SCS message or are sent one by one.

In single-message mode, WBM_MSG_INT is the time interval in milliseconds between assessments of the most suitable write bitmap message mode. In single-message mode, the writes issued by each remote node are, by default, sent one by one in individual SCS messages to the node with the master write bitmap. If the writes sent by a remote node reach an upper threshhold of messages during a specified interval, single-message mode switches to buffered-message mode.

In buffered-message mode, WBM_MSG_INT is the maximum time a message waits before it is sent. In buffered-message mode, the messages are collected for a specified interval and then sent in one SCS message. During periods of increased message traffic, grouping multiple messages to send in one SCS message to the master write bitmap is generally more efficient than sending each message separately.

The minimum value of WBM_MSG_INT is 10 milliseconds. The maximum value is -1, which corresponds to the maximum positive value that a longword can represent. The default is 10 milliseconds.

WBM_MSG_LOWER (D)

WBM_MSG_LOWER is one of three system parameters that are available for managing the update traffic between a master write bitmap and its corresponding local write bitmaps in an OpenVMS Cluster system. The others are WBM_MSG_INT and WBM_MSG_UPPER. These parameters set the interval at which the frequency of sending messages is tested and also set an upper and lower threshold that determine whether the messages are grouped into one SCS message or are sent one by one.

WBM_MSG_LOWER is the lower threshold for the number of messages sent during the test interval that initiates single-message mode. In single-message mode, the writes issued by each remote node are, by default, sent one by one in individual SCS messages to the node with the master write bitmap. If the writes sent by a remote node reach an upper threshhold of messages during a specified interval, single-message mode switches to buffered-message mode.

The minimum value of WBM_MSG_LOWER is 0 messages per interval. The maximum value is -1, which corresponds to the maximum positive value that a longword can represent. The default is 10.

WBM_MSG_UPPER (D)

WBM_MSG_UPPER is one of three system parameters that are available for managing the update traffic between a master write bitmap and its corresponding local write bitmaps in an OpenVMS Cluster system. The others are WBM_MSG_INT and WBM_MSG_LOWER. These parameters set the interval at which the frequency of sending messages is tested and also set an upper and lower threshold that determine whether the messages are grouped into one SCS message or are sent one by one.

WBM_MSG_UPPER is the upper threshold for the number of messages sent during the test interval that initiates buffered-message mode. In buffered-message mode, the messages are collected for a specified interval and then sent in one SCS message.

The minimum value of WBM_MSG_UPPER is 0 messages per interval. The maximum value is -1, which corresponds to the maximum positive value that a longword can represent. The default is 20 seconds.

WBM_OPCOM_LVL (D)

WBM_OPCOM_LVL controls whether write bitmap system messages are sent to the operator console. Possible values are shown in the following table:
Value Description
0 Messages are turned off.
1 The default; messages are provided when write bitmaps are started, deleted, and renamed, and when the SCS message mode (buffered or single) changes.
2 All messages for a setting of 1 are provided plus many more.

WINDOW_SYSTEM (D)

WINDOW_SYSTEM specifies the windowing system to be used on a workstation. Specify one of the following values:
Value Description
1 Load the DECwindows Motif for OpenVMS workstation environment.
2 Load the UIS workstation environment.

WLKSYSDSK

(Alpha and I64) WLKSYSDSK is used by various bootstrap components to determine if the system disk should be treated as though it is write-locked. This parameter is used primarily to allow OpenVMS to boot from a CD.

WPRE_SIZE (D)

WPRE_SIZE represents the number of pages to be allocated to accommodate WatchPoint Recovery Entries (WPRE) on the Watchpoint Driver.

This special parameter is used by HP and is subject to change. Do not change this parameter unless HP recommends that you do so.

WPTTE_SIZE (D)

WPTTE_SIZE is the number of entries that the WPDRIVER creates in the WatchPoint Trace Table.

This special parameter is used by HP and is subject to change. Do not change this parameter unless HP recommends that you do so.

WRITABLESYS

WRITABLESYS controls whether system code is writable. This parameter is set (value of 1) for debugging purposes only.

This special parameter is used by HP and is subject to change. Do not change this parameter unless HP recommends that you do so.

WRITESYSPARAMS (D)

On VAX systems, WRITESYSPARAMS indicates that parameters are modified during SYSBOOT and are written out to VAXVMSSYS.PAR by STARTUP.COM.

On Alpha and I64 systems, WRITESYSPARAMS indicates that parameters are modified during SYSBOOT and are written out to ALPHAVMSSYS.PAR by STARTUP.COM.

This special parameter is used by HP and is subject to change. Do not change this parameter unless HP recommends that you do so.

WSDEC (A,D,M)

Increasing the value of this parameter tends to increase the speed with which working set limits are decreased when the need arises.

On VAX systems, WSDEC specifies the number of pages by which the limit of a working set is automatically decreased at each adjustment interval (which is quantum end). At a setting of 35, for example, the system decreases the limit of a working set by 35 pages each time a decrease is required.

On Alpha and I64 systems, WSDEC specifies the number of pagelets by which the limit of a working set is automatically decreased at each adjustment interval (which is quantum end). At a setting of 35, for example, the system decreases the limit of a working set by 35 pagelets each time a decrease is required.

WSINC (A on Alpha and I64,D,M)

Decreasing the value of this parameter tends to reduce the speed with which working set limits are increased when the need arises. Normally, you should keep this parameter at a high value because a rapid increase in limit is often critical to performance.

On VAX systems, WSINC specifies the number of pages by which the limit of a working set is automatically increased at each adjustment interval (which is quantum end). At a setting of 150, for example, the system increases the limit of a working set by 150 pages each time an increase is required. On VAX systems, the default value is 150 512-byte pages.

On Alpha and I64 systems, WSINC specifies the number of pagelets by which the limit of a working set is automatically increased at each adjustment interval (which is quantum end). At a setting of 150, for example, the system increases the limit of a working set by 150 pagelets each time an increase is required. On Alpha and I64 systems, the default value is 2400 512-byte pagelets (150 8192-byte Alpha and I64 pages).

A value of 0 for WSINC disables the automatic adjustment of working set limits for all processes. Limits stay at their base values. You can disable the automatic adjustment of working set limits on a per-process basis by using the DCL command SET WORKING_SET.

WSMAX (A,G,M)

WSMAX sets the maximum number of pages on a systemwide basis for any working set. WSMAX is calculated as a quarter of the first 32 MB plus a sixteenth of the memory from 32 to 256 MB, plus a sixty-fourth of the memory (if any) above 256 MB.

This is intended to assist managers of systems that host large numbers of users whose working sets are not large. Systems whose user bases consist of a small number of users (or processes) that require large amounts of physical memory (for example, simulations) might need to set MIN_WSMAX to a value that satisfies the requirements of those processes.

WS_OPA0

(VAX only) WS_OPA0 enables OPA0 output to the QVSS screen for a workstation. A value of 1 enables output for OPA0 to the QVSS screen; a value of 0 causes output for OPA0 to be ignored.

XQPCTL2

XQPCTL2 controls improved concurrency. The default value of XQPCTL2 is 1, which turns on improved concurrency. Setting XQPCTL2 to 0 turns off improved concurrency. This parameter affects local access to the extent and file ID caches.

This special parameter is used by HP and is subject to change. Do not change this parameter unless HP recommends that you do so.

XQPCTLD1

XQPCTLD1 controls multithreading, which can be used only by PATHWORKS servers. The default value of XQPCTLD1 is 8, which enables multithreading. Setting XQPCTLD1 to 0 disables multithreading,

This special parameter is used by HP and is subject to change. Do not change this parameter unless HP recommends that you do so.

ZERO_LIST_HI (A,D)

(Alpha and I64) ZERO_LIST_HI is the maximum number of pages zeroed and put on the zeroed page list. This list is used as a cache of pages containing all zeros, which improves the performance of allocating such pages.


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