This command displays information about the total amount of space available in the DASD buffer, percentage in use and how much DASD buffer space each Externalization Server subgroup queue is holding for not yet Externalized Virtual Volumes. Only subgroups with Virtual Volumes queued for Externalization will be displayed by default.
SVTn Display Groups [,{Detail | All}]
Display information by queued location, Global VCAT and Local VCAT.
Display detailed information for all groups regardless of whether they have Virtual Volumes queued for Externalization.
Example of information displayed by the DISPLAY GROUPS command
SVT5 D G SVT5X0300I Display Group Information Max Drives=0008, Thresholds Warning=099%, Hold=030%, Release=050% Schedule=(00:00-23:59), Active Dasd cache utilization 00029775/00028303/00002001 InUse=088% Group Status Queue #Vols MB.Used MB.Alloc Dasd% MB.Thold Prty ----- ------- ------ ----- -------- -------- ----- -------- ---- 11.L *Act(3) All 5 8984 8989 30% 1000 1.0 33.L *Act(2) All 2 4000 4002 13% 1000 2.0 51.S *Rlse All 2 4000 4002 13% 1000 1.0 Totals: 9 16984 16993 57% An asterisk (*) in the Status column indicates an automated queue
SVT5X0100I Command Complete
Example of information displayed by the DISPLAY GROUPS,Detail command
SVT5 D G,D SVT5X0300I Display Group Information Max Drives=0008, Thresholds Warning=099%, Hold=030%, Release=050% Schedule=(00:00-23:59), Active Dasd cache utilization 00029775/00028871/00004002 InUse=083% Group Status Queue #Vols MB.Used MB.Alloc Dasd% MB.Thold Prty ----- ------- ------ ----- -------- -------- ----- -------- ---- 11.L *Act(3) Local 3 5100 5103 17% 1000 1.0 Global 1 1884 1885 6% 33.L *Act(2) Local 2 4000 4002 13% 1000 2.0 51.S *Rlse Local 1 2000 2001 7% 1000 1.3 Global 1 2000 2001 7% Totals: 8 14984 14992 50%
The following list describes the information displayed in examples above:
The maximum number of drives the Backstore Engine can use concurrently.
The cache InUse percentage at which to start and stop issuing the SVTnD0908I warning message. This percentage value is defined in parmlib using the CacheWarningThreshold attribute.
The cache InUse percentage at which the Automated Subgroup queues are held. This percentage value is defined in parmlib using the CacheAutoHoldLowThreshold attribute.
The cache InUse percentage at which the Automated Subgroup queues should be released. This percentage value is defined in parmlib using the CacheAutoReleaseHighThreshold attribute.
The times when the Automated Subgroup queues can be released followed by a state value. The schedule is defined in parmlib using the CacheAutomationSchedule attribute.
The current state of Externalization Subgroup Automation as follows:
Means it is not configured.
Means it is configured and within a configured time period that allows automated subgroup queues to be released and held.
Means it is configured, but not in a configured time period that allows automated subgroup queues to be released and held.
Megabytes of total shared DASD buffer space defined to CA Vtape (Total Cache).
Megabytes of DASD buffer space populated with Virtual Volumes (Populated Cache).
Megabytes of DASD buffer space that have been Externalized and can therefore be freed for reuse (Freeable Cache).
Percentage of shared DASD buffer space that cannot be freed for reuse because it has not been Externalized. The percentage is calculated as follows:
Populated Cache - Freeable Cache
InUse = ---------------------------------- x 100
Total Cache
Describes the group and subgroup associated with an Externalization Server queue as nn.x, where nn is the group number while x is the subgroup (S=short, M=medium, L=long). Group 255 is not included because it does not have an Externalization Server queue.
Describes the current status of the Externalization queue as seen by the Externalization Server running on this system as follows:
Indicates that the queue is currently held.
Indicates that the queue has been released but that no active tasks are running.
Indicates that no drives are available for the esoteric or generic defined for this group.
Indicates that the Externalization Server started (n) tasks for this queue.
A leading asterisk indicates a queue associated with an automated subgroup whose status is automatically controlled by parmlib settings. In the preceding example, *Act(3) is an active queue associated with the automated subgroup 11.L with three active tasks. Queues not associated with Automated Subgroups are manually controlled by the operator using the SVTn SET BACKSTORE command.
Describes where the work element is currently queued. A Virtual Volume that needs to be Externalized is first queued in the Local VCAT. After a waiting period of 30 to 60 seconds to ensure that the Virtual Volume is not mounted by the next application job step or job, the queue element is moved to the Global VCAT. When the Virtual Volume is about to be Externalized, the queue element is moved back to the Local VCAT of the subsystem doing the Externalization.
For SVTn D G, the subgroup's local and global queues are combined into a single line and the queue is shown as All.
For SVTn D G,A | D, the subgroup's local queues are always displayed. The global queues are only displayed if there are Virtual Volumes waiting to be Externalized.
Describes the number of Virtual Volumes needing to be Externalized. The global queue holds one entry for each Virtual Volume. The local queue, however, temporarily holds one entry each time a Virtual Volume that was updated is dismounted. If the same Virtual Volume is updated by mounting and dismounting it three times, #Vols for the local queue will be incremented three times, once for each update.
Describes the actual number of megabytes written to DASD for Virtual Volumes needing to be Externalized.
Describes the number of megabytes allocated on DASD to hold the data written to the Virtual Volumes needing to be Externalized.
Describes the percentage of DASD buffer occupied by the Virtual Volumes needing to be Externalized.
Describes the subgroup megabyte threshold defined in Parmlib with the MB_Threshold attribute. It is used to determine how many Externalization subtasks need to be started to service a subgroup queue.
Describes the Externalization priority for the subgroup as X.Y, where X is a user priority value between 0 to 9 (lowest to highest) as established in parmlib with the BackstorePriority attribute. Y is a value between 0 and 8, which is a dynamically calculated priority based on MB.Used/MB.Thold to determine the number of subtasks required to service this queue. Assuming enough tape drives are available, the Externalization queue with the highest priority is serviced first.
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