Chapter 4. SMS and its interactions with DFSMShsm
4.4 Management class
The
management class
that is assigned to a data set is the primary factor that determines how DFSMShsm treats a data set. Only SMS-managed DASD data sets are assignedmanagement classes. Management classes define the following attributes for a data set:
Expiration
Partial release
Migration
Special processing for generation data sets (GDSs)
Backup
Aggregate backup and recovery support (ABARs)
DGTDCSGA TAPE STORAGE GROUP ALTER Command ===> SCDS Name . . . : SYS1.SMS.MHLRES3.SCDS Storage Group Name : SGLIB1 To ALTER Storage Group, Specify: Description ==> ==> Library Names (1 to 8 characters each): ===> LIB1 ===> ===> ===> ===> ===> ===> ===> ALTER SMS Storage Group Status . . N (Y or N) Use ENTER to Perform Verification and Selection;
Chapter 4. SMS and its interactions with DFSMShsm 65
4.4.1 Expiration
Three attributes together determine whether a data set is eligible to be expired. These values apply to DASD data sets based on the management class that is assigned to the data set. These values can also influence the life of tape data sets. For DASD data sets, expiration processing is performed as part of primary space management. For tape data sets, expiration is performed by your tape management system.
The following attributes define whether a data set expires:
Expire after days non-usage
Expire after date/days
Retention limit
The default value for each of these settings is NOLIMIT.
Figure 4-3 shows the first page of the Management Class Alter panel.
Figure 4-3 ISMF Management Class Alter panel
DFSMShsm uses a combination of the three values to determine whether or when a DASD data set is eligible for expiration.
Expire after days non-usage
This attribute determines how many days will elapse after the last use of the data set before it is eligible to be expired. The data set’s last use is determined by the last reference date in the volume table of contents (VTOC) (DS1REFD in the format1 or format8 data set control block (DSCB)).
Expire after date/days
This attribute defines either the actual date on which a data set becomes eligible for expiration, or the absolute number of days after its initial allocation that a data set becomes eligible for expiration.
DGTDCMC1 MANAGEMENT CLASS ALTER Page 1 of 5 Command ===> SCDS Name . . . : SYS1.SMS.MHLRES3.SCDS Management Class Name : MC365 To ALTER Management Class, Specify: Description ==> ==> Expiration Attributes Expire after Days Non-usage . . 365 (1 to 93000 or NOLIMIT) Expire after Date/Days . . . NOLIMIT (0 to 93000, yyyy/mm/dd or NOLIMIT) Retention Limit . . . NOLIMIT (0 to 93000 or NOLIMIT) Use ENTER to Perform Verification; Use DOWN Command to View next Panel;
Retention limit
If you specify a value for the retention limit attribute other than NOLIMIT, you can restrict the values that users can specify for data sets at allocation time. A user-specified value for retention period (RETPD) or expiration date (EXPDT) can be accepted, reduced, or removed entirely. If NOLIMIT is specified for the retention period, any RETPD or EXPDT that is assigned to a data set is accepted. If the user-specified value for RETPD or EXPDT is less than the value that is specified in the retention limit, it is accepted and assigned to the data set. If the retention limit is set to zero, any RETPD or EXPDT value that the user assigns to a data set is overridden.
Interaction between expiration and retention
The following rules are followed for both tape and DASD data sets:
If both expiration attributes are NOLIMIT, the data set never expires. The setting of RETPD has no impact.
If the retention period is zero, neither of the settings for expiration has any impact and the data set will not expire.
If the retention period is not zero and one of the expiration attributes is NOLIMIT and the other is specified, the specified value is used and the data set expires.
If the date that is determined by the expiration values is sooner than the retention period, both expiration attributes must be satisfied. The data set expires on the latter of the dates that are determined by the expiration attributes.
Recommendations
In general, we recommend not using expiration dates for DASD data sets and setting RETPD to zero in management classes. This approach ensures that data sets are managed by DFSMShsm while they are cataloged, and that any EXPDT or RETPD values that are coded at data set allocation are ignored.
For DFSMShsm tape data sets, we recommend not specifying a retention period or expiration date unless your tape management system treats this date as a non-expiration flag. This topic is described more in Chapter 7, “Tape considerations” on page 117.
4.4.2 Partial release
This attribute determines whether DFSMShsm releases allocated but unused space for data sets that are assigned to this management class. This attribute is only relevant to non-Virtual Storage Access Method (VSAM) data sets and to extended format VSAM data sets.
The following values are valid for the partial release attribute:
N Partial release is not performed. N is the default value.
Y Space is released during primary space management.
C Partial release is performed only if a secondary allocation exists for the data set.
YI Partial release is performed either during primary space management or whenever the data set is closed.
CI Partial release is performed either during primary space management or whenever the data set is closed, but only if a secondary allocation exists for the data set.
Chapter 4. SMS and its interactions with DFSMShsm 67
If you plan to use partial release, consider using the options that occur only if a secondary allocation is present. If a data set with only a primary allocation is processed by partial release, any attempt to later extend the data set fails.
4.4.3 Migration
Your management classes define how DFSMShsm targets data sets during space
management, determining what data sets are migrated and to which level they are migrated. You can control DFSMShsm migration processing by using management class attributes. Figure 4-4 shows the ISMF Management Class Alter panel where these attributes are defined.
Figure 4-4 ISMF Management Class Alter panel
Primary days non-usage
This attribute determines how many days after a data set is not accessed, based on DS1LREFD, until a data set is eligible to be migrated. You can specify a value 0 - 9999. A value for this field is required if the Command or Auto Migrate attribute is set to Yes. The default value is 2.
Level 1 days non-usage
This setting determines whether data sets are migrated to DFSMShsm ML1 media, and if so, how long they remain on level 1 media. The default value is 60. The following values are valid:
Zero A 0 indicates no migration to DFSMShsm ML1. If migration occurs, data sets are migrated directly to DFSMShsm ML2.
A number of days 1 - 9999
The total number of days since the last access to the data set before the data set is eligible to be moved to ML2. This period includes any time that is spent on primary DASD before the data set was moved to ML1.
DGTDCMC2 MANAGEMENT CLASS ALTER Page 2 of 5 Command ===> SCDS Name . . . : SYS1.SMS.MHLRES3.SCDS Management Class Name : MC365 To ALTER Management Class, Specify: Partial Release . . . YI (Y, C, YI, CI or N) Migration Attributes Primary Days Non-usage . . . . 10 (0 to 9999 or blank) Level 1 Days Non-usage . . . . 30 (0 to 9999, NOLIMIT or blank) Command or Auto Migrate . . . . BOTH (BOTH, COMMAND or NONE) GDG Management Attributes # GDG Elements on Primary . . . 2 (0 to 255 or blank) Rolled-off GDS Action . . . EXPIRE (MIGRATE, EXPIRE or blank) Use ENTER to Perform Verification; Use UP/DOWN Command to View other Panels;
NOLIMIT Data sets will not move from ML1 to ML2 during automated DFSMShsm processing. They remain on ML1. Data sets can be moved with storage administrator commands, such as a FREEVOL command.
For more information about using the FREEVOL command, see “Converting level 1 DASD volumes” on page 334.
Command or Auto Migrate attribute
This attribute determines whether data sets are eligible to be processed by DFSMShsm automated functions or by command only. Commands can be generated either by storage administrators or users unless migration is prohibited for this data set. The possible values are BOTH, COMMAND, or NONE. If NONE is specified, data sets will not migrate and you can leave the “primary days non-usage” and “level 1 days non-usage” fields blank.
4.4.4 GDG management
The following generation data group (GDG) management criteria apply only for GDS data sets. They apply in addition to the normal migration attributes. You can specify the following attributes in ISMF. Figure 4-4 on page 67 shows the ISMF Management Class Alter panel where these options are defined.
# GDG Elements on Primary attribute
This attribute determines the number of GDS data sets for the GDG base on the primary DASD. Additional GDS data sets are targeted by DFSMShsm for migration. Possible values are 0 - 255, or blank. The default is blank. DFSMShsm targets older GDS data sets for migration. Older generations are migrated even if they do not meet the normal migration criteria for the management class.
Rolled-off GDS Action attribute
If a GDG is defined with the NOSCRATCH option, older GDS data sets will not be scratched as they are rolled out of the GDG base. Rolled-off GDS action applies only to those data sets. The following values are valid:
MIGRATE Rolled-off GDS data sets are targeted for migration by using the management class Migration attributes.
EXPIRE Rolled-off GDS data sets are expired.
None No action is taken.
If a GDG is defined with the SCRATCH attribute, these settings have no meaning.
4.4.5 Backup attributes
The following attributes of a management class are used by DFSMShsm backup processing:
Backup Frequency
Number of Backup Vers (Data Set Exists)
Number of Backup Vers (Data Set Deleted)
Retain days only Backup Ver (Data Set Deleted)
Retain days extra Backup Vers
Admin or User Command Backup
Auto Backup
Chapter 4. SMS and its interactions with DFSMShsm 69
Figure 4-5 shows the portion of the ISMF Management Class Alter panel where these values are specified.
Figure 4-5 ISMF Management Class Alter panel
Backup Frequency attribute
This attribute determines how many days can elapse before DFSMShsm backs up a changed data set. The default value is 1. To back up a changed data set every backup cycle, specify the backup frequency as zero.
Number of Backup Vers (Data Set Exists) attribute
This attribute specifies the maximum number of backup copies for a data set that can exist while the source data set exists. The default value is 2.
Number of Backup Vers (Data Set Deleted) attribute
This attribute specifies the maximum number of backup copies that can be kept when EXPIREBV processing determines that the source data set was deleted. For more information about EXPIREBV processing, see 11.1.6, “Expiring backup versions” on page 328. The default value is 1.
Retain days only Backup Ver (Data Set Deleted) attribute
This attribute determines how long DFSMShsm keeps the most recent backup version of a data set when EXPIREBV processing determines that the original data set was deleted. If the value that is specified for “retain days extra backup versions” is NOLIMIT, all backup versions are kept for this period. The possible values for this field are a number of days (1 - 9999) or
NOLIMIT. If NOLIMIT is set, backups are kept until they are manually deleted. The default value is 60.
DGTDCMC3 MANAGEMENT CLASS ALTER Page 3 of 5 Command ===> SCDS Name . . . : SYS1.SMS.MHLRES3.SCDS Management Class Name : MC365 To ALTER Management Class, Specify: Backup Attributes Backup Frequency . . . 1 (0 to 9999 or blank) Number of Backup Vers . . . 10 (1 to 100 or blank) (Data Set Exists) Number of Backup Vers . . . 2 (0 to 100 or blank) (Data Set Deleted) Retain days only Backup Ver . . . 60 (1 to 9999, NOLIMIT or blank) (Data Set Deleted) Retain days extra Backup Vers . . 20 (1 to 9999, NOLIMIT or blank) Admin or User command Backup . . BOTH (BOTH, ADMIN or NONE) Auto Backup . . . Y (Y or N) Backup Copy Technique . . . S (P, R, S, VP, VR, CP or CR)
Retain days extra Backup Vers attribute
This field applies to other than the most recent backup copy of a data set. It determines how long to keep backup copies other than the most recent backup copy. The value is specified as a number of days (1 - 9999). Or, NOLIMIT can be specified, in which case no backup copies are expired until the number of backups exceeds the specified number of backup versions. The default value is 30.
If a value other than NOLIMIT is specified, fewer than the expected number of backup versions for a fairly static data set are possible because older versions are expired and no new backup is created if the data set is not changed.
Admin or User command Backup attribute
This setting determines whether users, DFSMShsm administrators, or both, can explicitly issue data set level backups against the data sets. The following values are valid for this setting:
NONE Data set backup commands that are issued against data sets that are assigned to this management class are not processed.
ADMIN Data set backup commands that are issued against data sets by DFSMShsm storage administrators are processed. Commands from users are failed.
BOTH Both storage administrators and users can issue DFSMShsm backup commands against data sets that are assigned to this management class.
The default value is BOTH.
Auto Backup attribute
This parameter specifies whether or not DFSMShsm Autobackup processing targets data sets with this management class. The possible values are Y or N. Y is the default value.
Backup Copy Technique attribute
This parameter works together with the storage class accessibility value and the physical DASD where the data set exists. These values are used for both automatic and
user-generated backup copies. Nine values are valid:
R Concurrent Required. Concurrent Copy must be used for data set backup. Backups fail if Concurrent Copy cannot be used.
P Concurrent Preferred. DFSMShsm first attempts to perform the backup by using Concurrent Copy. If this attempt fails, it then selects a non-Concurrent Copy technique to back up the data set.
S Standard. Data sets are backed up without using Concurrent Copy.
VP Virtual Preferred. Virtual Concurrent Copy is preferred. If virtual Concurrent Copy is not available, standard copy techniques are used.
VR Virtual Required. Virtual Concurrent Copy is to be used. If virtual Concurrent Copy fails, the data set backup is failed.
CP Cache Preferred. Data is processed with cache-based Concurrent Copy if available; otherwise, standard copy techniques are used.
CR Cache Required. Data is processed with cache-based Concurrent Copy if available; otherwise, the data set is not backed up.
Chapter 4. SMS and its interactions with DFSMShsm 71
4.4.6 ABARS attributes
The following management class attributes apply only if you plan to use the DFSMShsm ABARs facility:
# Versions
Retain Only Version
Retain Extra Versions
Copy Serialization
Abackup Copy Technique
Figure 4-6 is a sample ISMF Management Class Alter panel with specified ABARS attributes.
Figure 4-6 ISMF Management Class Alter panel
You can define the following attributes. These attributes apply to the aggregate group, not to the data sets that are part of the group.
# Versions attribute
This attribute determines the number of versions of an aggregate group that DFSMShsm retains. The field is not required. The specified value can be a number (1 - 9999) or NOLIMIT. By default, no value is specified.
Retain Only Version attribute
This attribute defines how long the only version of an Abackup is retained. The value is a number (1 - 9999) or NOLIMIT, which means that the most recent version of an aggregate is retained for an unlimited time. The default value is a blank, which results in the most recent or only version of an aggregate being expired. If you specify a numeric value, you can also specify a unit: days, weeks, months, or years that are applied to the numeric value. If a non-blank value is specified, “Retain Only Version, Unit” becomes a required field.
DGTDCMC7 MANAGEMENT CLASS ALTER Page 5 of 5 Command ===> SCDS Name . . . : SYS1.SMS.MHLRES3.SCDS Management Class Name : MC365 To ALTER Management Class, Specify: AGGREGATE Backup Attributes: # Versions . . . (1 to 9999, NOLIMIT or blank) Retain Only Version . . . (1 to 9999, NOLIMIT or blank) Unit . . . (D=days, W=weeks, M=months, Y=years or blank) Retain Extra Versions . . (1 to 9999, NOLIMIT or blank) Unit . . . (D=days, W=weeks, M=months, Y=years or blank) Copy Serialization . . . . (C=continue, F=fail or blank) Abackup Copy Technique . . S (P, R, S, VP, VR, CP or CR) Use ENTER to Perform Verification; Use UP Command to View previous Panel;
Retain Extra Versions attribute
This attribute defines how long aggregate versions other than the most recent version are retained. The value is a number (1 - 9999) or NOLIMIT, which means that the most recent version of an aggregate is retained for an unlimited time. The default value is a blank, which results in the most recent, or only version of an aggregate being expired. If you specify a numeric value, you can also specify a unit: days, weeks, months, or years that are applied to the numeric value. If a non-blank value is specified, “Retain Extra Versions, Unit” becomes a required field.
Copy Serialization attribute
The following values can be specified:C Continue. Allows aggregate backup to continue if a requested shared enqueue cannot be obtained.
F Fail. Aggregate backup fails if a requested enqueue cannot be obtained.
Blank Aggregate backup fails.
Abackup Copy Technique attribute
This parameter specifies the copy technique to use during ABACKUP processing. This value is independent of the copy technique that is used for other DFSMShsm backups. Nine values are valid:
R Concurrent Required. Concurrent Copy must be used for data set backup. Backups fail if Concurrent Copy cannot be used.
P Concurrent Preferred. DFSMShsm first attempts to perform the backup by using Concurrent Copy. If Concurrent Copy fails, it selects a non-Concurrent Copy technique to back up the data set.
S Standard. Data sets are backed up without using Concurrent Copy.
VP Virtual Preferred. Virtual Concurrent Copy is preferred. If virtual Concurrent Copy is not available, standard copy techniques are used.
VR Virtual Required. Virtual Concurrent Copy is to be used. If virtual Concurrent Copy fails, the data set backup is failed.
CP Cache Preferred. Data is processed with cache-based Concurrent Copy if available; otherwise, standard copy techniques are used.
CR Cache Required. Data is processed with cache-based Concurrent Copy. If cache-based Concurrent Copy fails, the data set is not backed up.
The default value is Standard.
4.5 Storage class
Assigning a storage class to a DASD data set is the trigger for a data set to be
SMS-managed. So, the act of assigning the storage class not only assigns the attributes of the storage class to the data set, but also affects how DFSMShsm processes the data set. When a data set is SMS-managed, the attributes that are assigned by the storage class, management class, and storage group data sets determine how DFSMShsm processes the data set rather than the DFSMShsm options that are established by using SETSYS commands.
Chapter 4. SMS and its interactions with DFSMShsm 73
Storage classes also specify several attributes that can directly affect how DFSMShsm processes a data set, for example:
Guaranteed space
Accessibility
Storage class attributes are defined in ISMF option 5. See Figure 4-7.
Figure 4-7 ISMF Storage Class Alter panel
Guaranteed space
Guaranteed space allows hand placement of data sets. It also changes the way that primary and secondary space allocations are distributed on multiple volume data sets. Guaranteed space also permits pre-allocation of space for data sets. Primary space is allocated on each volume. After primary space on a specific volume is used, as many secondary extents as