The storage group and management class are interrelated. The storage group Auto Migrate and Auto Backup parameters specify whether the volumes in this storage group are eligible to be processed automatically. The management class, assigned to the data sets residing on the volumes, determines whether and how to process the data sets on the volume. In contrast, if you set Auto Migrate or Auto Backup to N (No) in the storage group, the volumes in the storage group are not processed and data sets residing in the storage group are not migrated or backed up.

You can specify the following attributes on the Pool Storage Group Define panel:

Description

Is an optional field of 120 characters with which you can describe the pool storage group.

Auto Migrate

Specifies whether the DASD volumes in this storage group are eligible for automatic space management processing. Auto Migrate is a required field, which ISMF primes with the value Y (yes).

Y

(yes) specifies that data sets are eligible for primary space management and that DFSMShsm performs automatic space management if a processing window is defined to DFSMShsm. If the DFSMShsm system setting SETSYS INTERVALMIGRATION is specified, the data sets are eligible for interval migration. If the DFSMShsm system setting SETSYS ONDEMANDMIGRATION(Y) is specified, the data sets are eligible for on-demand migration and are not eligible for interval migration, even if SETSYS INTERVALMIGRATION is specified.

N

(no) specifies that data sets are not eligible for automatic migration.

I

(interval) specifies that data sets are eligible for primary space management and forces DFSMShsm to perform automatic interval migration independent of the DFSMShsm system setting for SETSYS INTERVALMIGRATION. Interval migration is performed on volumes that are at or above the high threshold only. Interval migration is performed hourly. If a low threshold value of 0 is specified, DFSMShsm migrates all eligible data sets in the selected storage group. DFSMShsm on-demand migration is not performed. This value is most useful for storage groups used with tape mount management.

P

(primary) specifies that data sets are eligible for primary space management. Interval migration and on-demand migration are not performed regardless of the DFSMShsm system setting for SETSYS INTERVALMIGRATION and SETSYS ONDEMANDMIGRATION.

Note: If for some reason (such as a system outage) system-managed temporary data sets are not deleted at the end of a job, DFSMShsm attempts to delete them during primary space management. In order for DFSMShsm to delete these data sets, you must specify Auto Migrate as Y, I or P.

Auto Backup

Specifies whether the DASD volumes in this storage group are eligible for automatic backup processing. Auto Backup is a required field, which ISMF primes with the value Y, yes. Y specifies that DFSMShsm backs up the data sets on the volume according to management class requirements.

Auto Dump

In Auto Dump, you specify whether you want to automatically dump all the DASD volumes in this storage group. It is an optional field, which ISMF primes with the value N, no. If you specify a value of Y, yes, DFSMShsm automatically dumps the volumes.

Migrate, Backup, and Dump Sys/Sys Group Name

ISMF no longer verifies that specified system or system group names are defined to the base configuration. You can specify either a system or a system group name in these fields but a specific system specified might not be defined in the configuration, because it might be defined as part of a system group. Therefore, if these fields are not blank, you must take special care to ensure that the values are correct. If the values are incorrect, it could result in the expected DFSMShsm operation not occurring.

DFSMShsm has the capability of processing each storage group for automatic space management, data availability management, and automatic dump processing. A system is eligible to perform the processing when any of the following are conditions are met:

• The name is blank, meaning any system can perform it
• The name specified is the name of the specific host system
• The name specified is the name of the system group to which the system belongs and the system is not individually defined by its system name in the configuration.

DFSMShsm ignores storage groups for which you specify a different system name, and does not process DASD volumes that have already been processed. Do not specify a Sys/Sys Group Name unless processing of the storage group for the function must be performed only on that one host because that limits the capabilities of DFSMShsm to perform the request.

The same rules apply to Backup Sys/Sys Group Name for data availability management processing, and to Dump Sys/Sys Group Name for automatic dump processing. All three Sys/Sys Group Name fields are optional and primed with blanks.

Overflow

Specifies whether this pool storage group is designated as an overflow storage group to handle periods of high demand for initial primary space allocations. Overflow is a required field, which ISMF primes with the value N (No). Y (Yes) specifies that the storage group is an overflow storage group.

To make overflow storage groups eligible for allocation, you must assign designated overflow storage groups in your storage group ACS routine.

If all volumes in a non-overflow storage group are so full that the current allocation request will push them over high threshold, while volumes in the overflow storage group are not so full, then the new data set will be allocated on a volume in the overflow storage group. The assumption is that all other attributes of the non-overflow storage group and overflow storage group and the volumes in those storage groups are the same.

During initial allocation, volumes in an overflow storage group are less preferred than volumes in an enabled storage group but more preferred than volumes in a quiesced storage group. Therefore, overflow volumes are not placed on the primary volume list but can be placed on the secondary volume list. When an overflow storage group contains more volumes than a buffer storage group, specified volume counts might result in overflow volumes being preferred over volumes in the buffer storage group.

An overflow storage group may also be specified as an extend storage group.

Volumes residing in overflow storage groups are preferred over quiesced volumes and storage groups. If you quiesce an overflow storage group or volume then the quiesced volumes are preferred over quiesced overflow volumes.

Extend SG Name

Specifies the name of another pool storage group to which data sets from the primary storage group can be extended when there is an insufficient amount of storage on the primary storage group. A primary storage group is the storage group in which the initial allocation resides.

Extend SG Name is an optional field of one-to-eight alphanumeric or national characters, or a combination, the first of which must be alphabetic. ISMF primes the field with the default value "blank."

You can define only one extend storage group to each storage group. However, you can define the same extend storage group to more than one primary storage group. Also, you can define two storage groups as extend storage groups of each other.

An extend storage group may also be specified as an overflow storage group.

Extend storage groups will not be used for initial allocation unless they are specified in the ACS routines. All storage groups that are listed in the ACS routines are candidates for initial allocation. Extend storage group attributes are not referenced during initial allocation.

Example: You can define storage group (SG) 3 as an extend of SG 2, and define SG 2 as an extend of SG 1. If SMS selects SG 1 as the primary storage group, the data set can extend only to SG 2. If SMS selects SG 2 as the primary storage group, the data set can extend only to SG 3.

For more information about data set extend in the volume selection process, see SMS volume selection for data set allocation.

Note:

1. Requirement: When you specify an extend storage group, you must ensure that connectivity across the SMSplex is the same for both the primary storage group and the extend storage group.
2. Because an extend storage group is a pool storage group, the SMS status also applies to the extend storage group.

Copy Pool Backup SG Name

Specifies the name of the copy pool backup storage group that contains eligible volumes for fast replication backup versions.

You can specify the name of a copy pool backup storage group that is shared by more than one pool storage group.

Copy Pool Backup SG Name is an optional field of one-to-eight alphanumeric or national characters, or a combination, the first of which must be alphabetic. ISMF primes the field with the default value of a blank name.

Dump Class

Specifies the name of a dump class that is defined in DFSMShsm. There are five Dump Class fields, so up to five unique dump class names may be specified.

When DFSMShsm dumps DASD volumes that belong to the storage group, it directs their contents to the dump classes. To use dump classes, you must first define their names and parameters using DFSMShsm. Then you can identify the dump class names to SMS using this panel.

Dump Class is an optional field. ISMF primes the field with the default value "blank."

DEFINE SMS Storage Group Status

Specifies whether you want to change the status of the pool storage group with respect to a given system in the SMS complex. Initially, the status is set to ENABLE for all. The values are

Y

Change a status. When you complete the current panel, you will see the SMS Storage Group Status Define panel. For more information, see Defining pool storage group status.

N

Leave all the status fields as ENABLE. This is the default.

Migration and Allocation Thresholds

Specifies an upper and lower space limit for the DASD volumes in a pool storage group.

SMS tries to stay within these thresholds by looking at the primary space allocation of each data set before assigning it to a given DASD volume. For example, the SMS volume selection function attempts to prevent allocation of a data set to a given DASD volume if that allocation causes the volume's high threshold to be exceeded. When a volume reaches or exceeds the high threshold, SMS issues an ENF72 signal, regardless of the Auto Migrate setting.

In addition, this high threshold value is used by DFSMShsm to determine whether data sets should be migrated off a DASD volume in the storage group. The low threshold value is used as the threshold goal in reducing the amount of space occupied on a DASD volume in the storage group during interval migration or daily space management. The low threshold value must be less than or equal to the high threshold value.

Both numbers are percentages of the total space on the DASD volume. If you specify Y for Auto Migrate, then you must specify both a high and low threshold. If you specify Y, the low threshold limit is 1. If you specify I for automatic interval migration, you can specify a low threshold value of 0 to migrate all the data sets in the selected storage group. The hourly migration trigger for storage groups with a value of AM=I is the occupancy at or above the midpoint of the high and low thresholds. Because storage groups used for tape mount management tend to fill up several times a day, allowing interval migration for these storage groups allows DFSMShsm to better keep up with the demand.

ISMF requires that you enter a high threshold value when you specify N for Auto Migrate, when defining a pool storage group. Because SMS needs the value for allocation purposes, the High Threshold field is a required field with a primed value of 85.

For a track-managed space of an extended address volume, the allocation and migration threshold specifies the threshold percentage of space allocation that triggers or stops migration of data sets from volumes in this storage group during interval migration. Valid values for high threshold are 1-100. Valid values for low threshold are 0-99. These fields are primed with default values and are ignored by SMS and DFSMShsm for other than extended address volumes. For the default values, refer to the ISMF help. If you alter an existing storage group to add extended address volume values, the specified bits are set to ON, when you specify the BreakPointValue and the Track Allocation Thresholds. If the specified indicators are not ON, SMS uses the existing threshold values, which represent threshold values for the entire volume, to represent threshold values for the track-managed space.

For more information about specifying allocation and migration thresholds, see z/OS DFSMShsm Storage Administration.

For more information about selecting appropriate threshold levels, see z/OS DFSMS Implementing System-Managed Storage.

Guaranteed Backup Frequency

Specifies the number of days within the last backup period in which the backup process should have a copy of each of the data sets within the applicable storage group. If Auto Backup is specified as Y, this attribute is required; otherwise it is optional.

You specify the maximum number of days that can elapse between backups. You can specify from 1 to 9999 days or you can specify NOLIMIT. If you specify NOLIMIT, then data sets in the storage group are backed up according to management class specifications. There is no default.

BreakPointValue

Specifies the number of cylinders (0-65520) that SMS uses to select volumes for VSAM data sets. You can specify BreakPointValue for each Storage Group separately. This keyword overrides the value in the IGDSMSxx PARMLIB member. If you do not specify this keyword, SMS assigns the default value of 10 cylinders. When SMS is not active, the system assigns the default value.

Processing Priority

Specifies the processing priority of the storage group. The value is in the range from 1 (lowest priority) to 100 (highest priority). It is used during DFSMShsm space management. The default is 50.