SET VDISK

Read syntax diagramSkip visual syntax diagram Set VDISKVDSKSyslimUserlimDefaultInfinitennnnnnnnnnBlocksBlksnnnnnnnMnnnnG

Authorization

Privilege Class: B

Purpose

Use SET VDISK to control the maximum amount of host real storage that is available for allocation as virtual disks in storage. Using virtual disks in storage increases the load on system paging, so you should set limits in proportion to the availability of paging space.

Operands

Syslim
sets the total resource available for allocating virtual disks in storage on the system.
Userlim
sets the maximum resource available for virtual disks in storage created by a single user using the DEFINE command. This limit does not apply to virtual disks in storage defined by MDISK statements in the directory.
Default
sets the limit to the default value. If an installation default is defined in the system configuration file, that value is used. If an installation default is not defined in the system configuration file, or if the file is not found, the built-in default is used, as follows:
  • The built-in default user limit is 0.
  • The built-in default system limit is the minimum of:
    • The amount of virtual storage that can be represented by one-quarter of the usable dynamic paging area (DPA), based on the fact that each gigabyte of virtual disk defined requires 2050 frames of host real storage
    • The amount of storage represented by one-quarter of the paging space defined for CP use
Infinite
indicates all available host real storage may be allocated to virtual disks in storage up to the limit of 2147483648 512-byte blocks.
nnnnnnnnnn Blocks
nnnnnnnnnn Blks
specifies the number of 512-byte blocks of host real storage available for virtual disks in storage. If the number specified is equal to or greater than 2147483648, the limit is set to INFINITE.
nnnnnnnM
specifies the number of megabytes of host real storage available for virtual disks in storage. If the number specified is equal to or greater than 1048576, the limit is set to INFINITE.
nnnnG
specifies the number of gigabytes of host real storage available for virtual disks in storage. If the number specified is equal to or greater than 1024, the limit is set to INFINITE.

Usage Notes

  1. Virtual disks in storage are allocated in 8-block (4096-byte) pages. Therefore, the actual limit that is set may be rounded up to the nearest page.
  2. If the system limit is set to a value that is less than the amount of host real storage currently allocated for virtual disks in storage, the command is accepted, but no new virtual disks in storage can be created until the total system usage drops below the limit. No currently-active virtual disks in storage are deleted. Any VDISK being created for a relocation in progress will not be subject to the new limit.
  3. If the user limit is set to a value that is less than the amount of host real storage currently allocated for virtual disks in storage created by the DEFINE command by a given user, the command is accepted, but that user cannot create any new virtual disks in storage with the DEFINE command until the user's total usage of virtual disks in storage created with the DEFINE command falls below the limit. No currently-active virtual disks in storage are deleted. Any VDISK being created for a relocation in progress will not be subject to the new limit.
  4. While virtual disks in storage can improve I/O performance, they may increase host real storage and paging resource requirements. Increasing the system and user limits increases the potential for end users to negatively impact system performance by using large virtual disks in storage improperly.
  5. Regardless of possible USERLIM INFINITE specifications, the maximum number of USERLIM blocks is limited by the maximum number of blocks permitted by the command "CP DEFINE VFB-512". For more information, see DEFINE (Virtual Disk in Storage).

Messages

  • HCP002E Invalid operand - operand
  • HCP003E Invalid option - [command contains extra option(s) starting with] option
  • HCP026E Operand missing or invalid