UPDATE STGPOOL (Update a copy sequential access storage pool)

Privilege class

To issue this command, you must have system privilege, unrestricted storage privilege, or restricted storage privilege for the storage pool to be updated.

Parameters

pool_name (Required)

Specifies the name of the copy storage pool to be updated.

DESCription

Specifies a description of the copy storage pool. This parameter is optional. The maximum length of the description is 255 characters. Enclose the description in quotation marks if it contains any blank characters. To remove an existing description, specify a null string ("").

ACCess

Specifies how client nodes and server processes (such as reclamation) can access files in the copy storage pool. This parameter is optional. Possible values are:

READWrite

Specifies that files can be read from and written to the volumes in the copy storage pool.

READOnly

Specifies that client nodes can read only files that are stored on the volumes in the copy storage pool.

Server processes can move files within the volumes in the storage pool. The server can use files in the copy storage pool to restore files to primary storage pools. However, no new writes are allowed to volumes in the copy storage pool from volumes outside the storage pool. A storage pool cannot be backed up to the copy storage pool.

UNAVailable

Specifies that client nodes cannot access files that are stored on volumes in the copy storage pool.

Server processes can move files within the volumes in the storage pool. The server can use files in the copy storage pool to restore files to primary storage pools. However, no new writes are allowed to volumes in the copy storage pool from volumes outside the storage pool. A storage pool cannot be backed up to the copy storage pool.

COLlocate

Specifies whether the server attempts to keep data, which is stored on as few volumes as possible, that belong to one of the following candidates:

• A single client node
• A group of file spaces
• A group of client nodes
• A client file space

This parameter is optional.

Collocation reduces the number of sequential access media mounts for restore, retrieve, and recall operations. However, collocation increases both the amount of server time that is needed to collocate files for storing and the number of volumes required.

You can specify one of the following options:

No

Specifies that collocation is disabled.

GRoup

Specifies that collocation is enabled at the group level for client nodes or file spaces. For collocation groups, the server attempts to put data for nodes or file spaces that belong to the same collocation group on as few volumes as possible.

If you specify COLLOCATE=GROUP but do not define any collocation groups, or if you do not add nodes or file spaces to a collocation group, data is collocated by node. Consider tape usage when you organize client nodes or file spaces into collocation groups.

For example, if a tape-based storage pool consists of data from nodes and you specify COLLOCATE=GROUP, the server completes the following actions:

• Collocates the data by group for grouped nodes. Whenever possible, the server collocates data that belongs to a group of nodes on a single tape or on as few tapes as possible. Data for a single node can also be spread across several tapes that are associated with a group.
• Collocates the data by node for ungrouped nodes. Whenever possible, the server stores the data for a single node on a single tape. All available tapes that already have data for the node are used before available space on any other tape is used.

If a tape-based storage pool consists of data from grouped file spaces and you specify COLLOCATE=GROUP, the server completes the following actions:

• Collocates by group, the data for grouped file spaces only. Whenever possible, the server collocates data that belongs to a group of file spaces on a single tape or on as few tapes as possible. Data for a single file space can also be spread across several tapes that are associated with a group.
• Collocates the data by node (for file spaces that are not explicitly defined to a file space collocation group). For example, node1 has file spaces named A, B, C, D, and E. File spaces A and B belong to a filespace collocation group but C, D, and E do not. File spaces A and B are collocated by filespace collocation group, while C, D, and E are collocated by node.

Data is collocated on the least amount of sequential access volumes.

NODe

Specifies that collocation is enabled at the client node level. For collocation groups, the server attempts to put data for one node on as few volumes as possible. If the node has multiple file spaces, the server does not try to collocate those file spaces. For compatibility with an earlier version, COLLOCATE=YES is still accepted by the server to specify collocation at the client node level.

If a storage pool contains data for a node that is a member of a collocation group and you specify COLLOCATE=NODE, the data is collocated by node.

FIlespace

Specifies that collocation is enabled at the file space level for client nodes. The server attempts to place data for one node and file space on as few volumes as possible. If a node has multiple file spaces, the server attempts to place data for different file spaces on different volumes.

REClaim

Specifies when the server reclaims a volume, which is based on the percentage of reclaimable space on a volume. Reclaimable space is the amount of space that is occupied by files that are expired or deleted from the Tivoli® Storage Manager database.

Reclamation makes the fragmented space on volumes usable again by moving any remaining active files from one volume to another volume, thus making the original volume available for reuse. This parameter is optional. You can specify an integer from 1 to 100. The value 100 means that reclamation is not completed.

When determining which volumes in a storage pool to reclaim, the Tivoli Storage Manager server first determines the reclamation threshold indicated by the RECLAIM. The server then examines the percentage of reclaimable space for each volume in the storage pool. If the percentage of reclaimable space on a volume is greater that the reclamation threshold of the storage pool, the volume is a candidate for reclamation.

For example, suppose storage pool FILEPOOL has a reclamation threshold of 70 percent. This value indicates that the server can reclaim any volume in the storage pool that has a percentage of reclaimable space that is greater that 70 percent. The storage pool has three volumes:

• FILEVOL1 with 65 percent reclaimable space
• FILEVOL2 with 80 percent reclaimable space
• FILEVOL3 with 95 percent reclaimable space

When reclamation begins, the server compares the percent of reclaimable space for each volume with the reclamation threshold of 70 percent. In this example, FILEVOL2 and FILEVOL3 are candidates for reclamation because their percentages of reclaimable space are greater than 70. To determine the percentage of reclaimable space for a volume, issue the QUERY VOLUME command and specify FORMAT=DETAILED. The value in the field Pct. Reclaimable Space is the percentage of reclaimable space for the volume.

If you change the value from the default of 100, specify a value of 50 percent or greater so that files stored on two volumes can be combined onto a single output volume.

When a copy pool volume that is offsite becomes eligible for reclamation, the reclamation process attempts to obtain the active files on the reclaimable volume from a primary or copy storage pool that is onsite. The process then writes these files to an available volume in the original copy storage pool. Effectively, these files are moved back to the onsite location. However, the files can be obtained from the offsite volume after a disaster if a database backup is used that references the files on the offsite volume. Because of the way reclamation works with offsite volumes, use it carefully with copy storage pools.

RECLAIMPRocess

Specifies the number of parallel processes to use for reclaiming the volumes in this storage pool. This parameter is optional. Enter a value from 1 to 999.

When calculating the value for this parameter, consider the number of sequential storage pools that will be involved with the reclamation and the number of logical and physical drives that can be dedicated to the operation. To access a sequential access volume, IBM® Tivoli Storage Manager uses a mount point and, if the device type is not FILE, a physical drive. The number of available mount points and drives depends on other Tivoli Storage Manager and system activity and on the mount limits of the device classes for the sequential access storage pools that are involved in the reclamation.

For example, suppose that you want to reclaim the volumes from two sequential storage pools simultaneously and that you want to specify four processes for each of the storage pools. The storage pools have the same device class. Each process requires two mount points and, if the device type is not FILE, two drives. (One of the drives is for the input volume, and the other drive is for the output volume.) To run eight reclamation processes simultaneously, you need a total of at least 16 mount points and 16 drives. The device class for each storage pool must have a mount limit of at least eight.

If the number of reclamation processes you specify is more than the number of available mount points or drives, the processes that do not obtain mount points or drives will wait for mount points or drives to become available. If mount points or drives do not become available within the MOUNTWAIT time, the reclamation processes will end. For information about specifying the MOUNTWAIT time, see DEFINE DEVCLASS (Define a device class).

The Tivoli Storage Manager server will start the specified number of reclamation processes regardless of the number of volumes that are eligible for reclamation. For example, if you specify ten reclamation processes and only six volumes are eligible for reclamation, the server will start ten processes and four of them will complete without processing a volume.

OFFSITERECLAIMLimit

Specifies the number of offsite volumes to have their space reclaimed during reclamation for this storage pool. This parameter is optional. Possible values are:

NOLimit

Specifies that you want to have the space reclaimed in all of your offsite volumes.

number

Specifies the number of offsite volumes to have their space reclaimed. You can specify an integer from 0 to 99999. A value of zero means that none of the offsite volumes will be reclaimed.

Important: When determining the value for the OFFSITERECLAIMLIMIT, consider using the statistical information in the message issued at the end of the offsite volume reclamation operation. Alternatively, you can use the following Tivoli Storage Manager SQL select command to obtain the statistical information from the SUMMARY table for the offsite volume reclamation operation:

select * from summary where activity='OFFSITE RECLAMATION'

The statistical information includes the following items:

• The number of offsite volumes that were processed
• The number of parallel processes that were used
• The total amount of time required for the processing

The order in which offsite volumes are reclaimed is based on the amount of unused space in a volume. (Unused space includes both space that has never been used on the volume and space that has become empty because of file deletion.) Volumes with the largest amount of unused space are reclaimed first.

For example, suppose a copy storage pool contains three volumes: VOL1, VOL2, and VOL3. VOL1 has the largest amount of unused space, and VOL3 has the least amount of unused space. Suppose further that the percentage of unused space in each of the three volumes is greater than the value of the RECLAIM parameter. If you do not specify a value for the OFFSITERECLAIMLIMIT parameter, all three volumes will be reclaimed when the reclamation runs. If you specify a value of 2, only VOL1 and VOL2 will be reclaimed when the reclamation runs. If you specify a value of 1, only VOL1 will be reclaimed.

MAXSCRatch

Specifies the maximum number of scratch volumes that the server can request for this storage pool. This parameter is optional. You can specify an integer from 0 to 100000000. By allowing the server to request scratch volumes as needed, you avoid having to define each volume to be used.

The value that is specified for this parameter is used to estimate the total number of volumes available in the copy storage pool and the corresponding estimated capacity for the copy storage pool.

Scratch volumes are automatically deleted from the storage pool when they become empty. However, if the access mode for a scratch volume is OFFSITE, the volume is not deleted from the copy storage pool until the access mode is changed. This allows an administrator to query the server for empty, offsite scratch volumes and return them to the onsite location.

When scratch volumes with the device type of FILE become empty and are deleted, the space that the volumes occupied is freed by the server and returned to the file system.

Tip: For server-to-server operations that use virtual volumes and that store a small amount of data, consider specifying a value for the MAXSCRATCH parameter that is higher than the value you typically specify for write operations to other types of volumes. After a write operation to a virtual volume, Tivoli Storage Manager marks the volume as FULL, even if the value of the MAXCAPACITY parameter on the device-class definition is not reached. The Tivoli Storage Manager server does not keep virtual volumes in FILLING status and does not append to them. If the value of the MAXSCRATCH parameter is too low, server-to-server operations can fail.

REUsedelay

Specifies the number of days that must elapse after all files are deleted from a volume before the volume can be rewritten or returned to the scratch pool. This parameter is optional. You can specify an integer from 0 to 9999. A value of 0 means that a volume can be rewritten or returned to the scratch pool as soon as all files are deleted from the volume.

Important: Use this parameter to help ensure that when you restore the database to an earlier level, database references to files in the copy storage pool are still valid. You must set this parameter to a value greater than the number of days you plan to retain the oldest database backup. The number of days that are specified for this parameter must be the same as the number specified for the SET DRMDBBACKUPEXPIREDAYS command.

OVFLOcation

Specifies the overflow location for the storage pool. The server assigns this location name to a volume that is ejected from the library by the MOVE MEDIA command. This parameter is optional. The location name can be a maximum length of 255 characters. Enclose the location name in quotation marks if the location name contains any blank characters.

To remove an existing value, specify a null string ("").

CRCData

Specifies whether a cyclic redundancy check (CRC) validates storage pool data when audit volume processing occurs on the server. This parameter is only valid for NATIVE data format storage pools. This parameter is optional. The default value is NO. By setting CRCDATA to YES and scheduling an AUDIT VOLUME command you can continually ensure the integrity of data that is stored in your storage hierarchy. Possible values are:

Yes

Specifies that data is stored containing CRC information, allowing for audit volume processing to validate storage pool data. This mode impacts performance because more processing is required to calculate and compare CRC values between the storage pool and the server.

No

Specifies that data is stored without CRC information.

Tip: For storage pools that are associated with the 3592, LTO, or ECARTRIDGE device type, logical block protection provides better protection against data corruption than CRC validation for a storage pool. If you specify CRC validation for a storage pool, data is validated only during volume auditing operations. Errors are identified after data is written to tape.

To enable logical block protection, specify a value of READWRITE for the LBPROTECT parameter on the DEFINE DEVCLASS and UPDATE DEVCLASS commands for the 3592, LTO, or ECARTRIDGE device types. Logical block protection is supported only on the following types of drives and media:

• IBM LTO5 and later.
• IBM 3592 Generation 3 drives and later with 3592 Generation 2 media and later.
• Oracle StorageTek T10000C and T10000D drives.

DEDUPlicate

Specifies whether the data that is stored in this storage pool is deduplicated. This parameter is optional and is valid only for storage pools that are defined with a FILE-type device class.

IDENTIFYPRocess

Specifies the number of parallel processes to use for server-side duplicate identification. This parameter is optional and is valid only for storage pools that are defined with a FILE device class. Enter a value from 1 to 50.

When calculating the value for this parameter, consider the workload on the server and the amount of data requiring data deduplication. Server-side duplicate identification requires disk I/O and processor resources, so the more processes you allocate to data deduplication, the heavier the workload that you place on your system. In addition, consider the number of volumes that require processing. Server-side duplicate-identification processes work on volumes containing data that requires deduplication. If you update a storage pool, specifying that the data in the storage pool is to be deduplicated, all the volumes in the pool require processing. For this reason, you might have to define a high number of duplicate-identification processes initially. Over time, however, as existing volumes are processed, only the volumes containing new data have to be processed. When that happens, you can reduce the number of duplicate-identification processes.

Remember: Duplicate-identification processes can be either active or idle. Processes that are working on files are active. Processes that are waiting for files to work on are idle. Processes remain idle until volumes with data to be deduplicated become available. The output of the QUERY PROCESS command for a duplicate-identification process includes the total number of bytes and files that have been processed since the process first started. For example, if a duplicate-identification process processes four files, becomes idle, and then processes five more files, then the total number of files processed is nine. Processes end only when canceled or when the number of duplicate-identification processes for the storage pool is changed to a value less than the number currently specified.