DFSMShsm Storage Administration Guide

This topic describes the tasks that must be performed to use DFSMShsm, a component of DFSMS that manages your storage in a hierarchical manner. It contains examples of the commands needed to perform the tasks, descriptions of the processing that DFSMShsm performs, and examples of the results of that processing.

Introduction

Welcome to DFSMShsm explains how to use this document and describes the functions of the DFSMShsm program, highlighting the following information:

The tasks that you perform to make DFSMShsm do useful work.
An overview of how DFSMShsm moves data.
How to use this document. You are introduced to the example system, which is referred to throughout the rest of this document.

Space management

The following topics introduce the tasks necessary to control space management functions. Space management is the DFSMShsm program function that you use to ensure that your customers have space available on DASD volumes to allocate new data sets or to extend old ones. You can make the space available by deleting data sets that have outlived their usefulness, removing unused allocated space from data sets, moving low-activity data sets from level 0 volumes to other DASD or tape volumes, and returning the moved data sets to the level 0 devices when the data sets are needed.

Space management of SMS-managed storage, describes the tasks to be performed and the results of processing for space management of data sets managed by the storage management subsystem (SMS).
Space management of non-SMS-managed storage, describes the tasks to be performed and the results of processing for space management of data sets not managed by SMS.
Other space management considerations, describes aspects of space management that deserve consideration but are peripheral to the discussions in the two preceding topics.
Space management procedures, describes procedures for starting and stopping space management under varying conditions.

Functions of space management:

Automatically delete, remove unused space from, and move data sets on DFSMShsm-managed volumes to provide a specified amount of free space on each volume. The space management functions begin at a specified time of day and only on a specific day of a cycle. This operation is called automatic primary space management. The process of removing unused space from the data sets is called space reduction. Moving the data sets (as opposed to deleting or removing unused space from them) is called migration.
Reconnect unchanged data sets that are recalled from ML2 tapes to their original ML2 tapes with the fast subsequent migration function.
Ensure that a specified amount of space is available on DFSMShsm-managed volumes. If DFSMShsm finds any volume without the specified amount of space, it performs migration from all such volumes (known as event-driven migration) following a space check.
Automatically clean up migration volumes and the migration control data set (MCDS). This function and the following one are known as automatic secondary space management.
Automatically, or by command, migrate data sets from level 1 migration volumes to level 2 migration volumes.
Automatically recall needed migrated data sets to level 0 volumes.
Recall migrated data sets to level 0 volumes by command.
Delete eligible data sets on a non-SMS-managed volume by command.
Delete eligible non-SMS migrated data sets on a migration volume by command.
Migrate individual data sets or eligible data sets on a volume by command.

Availability management

The following topics introduce the tasks necessary to control availability management functions. Availability management is the function of the DFSMShsm program that you use to ensure that your customers can retrieve usable copies of their data sets should their online copies become lost or damaged. You can make the copies available by making daily incremental backup copies of changed data sets, making periodic dump copies of the DFSMShsm-managed and ML1 volumes, making aggregate backup copies of data sets that your operation will need if your installation is damaged, and making fast replication backup versions for sets of storage groups.

Availability management of SMS-managed storage, which describes the tasks to be performed and the results of processing for availability management of data sets managed by SMS.
Availability management of non-SMS-managed storage, which describes the tasks to be performed and the results of processing for availability management of data sets not managed by SMS.
Aggregate backup and recovery support (ABARS), which describes the command-driven functions that back up and recover a user-defined group (aggregate group) of data sets.
Making disaster backup copies of DFSMShsm-owned tape volumes, which describes how to make backup copies of DFSMShsm-owned, cartridge-type, single-file-format tape volumes and how to recover those volumes.
Other availability management considerations, which describes aspects of availability management that deserve consideration but are peripheral to the discussions in the preceding topics.
Availability management procedures, which describes procedures for starting and stopping availability management under varying conditions.

Functions of availability management:

Automatically make backup copies of individual changed data sets on DFSMShsm-managed volumes. This is known as incremental backup. You can specify how frequently to back up data sets on a data set basis for SMS-managed data sets and on a system-wide basis for non-SMS-managed volumes. You can specify on a system-wide basis how often backup runs.
Automatically make dump copies of DFSMShsm-managed level 0 volumes and ML1 volumes on a specified schedule for day and time. You can dump different groups of volumes on different days with different periods for the number of days between dumps.
Allow your customers to issue commands to recover their own data sets.
Allow your customer to issue the HBACKDS command from a batch environment. See Inline backup.
By command, back up user data sets.
By command, back up data sets of an application to tape so they can be taken to another computer site for recovery.
By command, recover user data sets or data sets of an application to their original system environment at another computer site.
By command, restore a volume from a dump copy and update the restored volume from later incremental backup versions.
By command, recover a specific data set from either a dump copy or an incremental backup version.
By command, create a fast replication backup of a copy pool.
Automatically or by command, create a dump copy of a fast replication DASD backup version
By command, recover volumes that have a fast replication backup version.
By command, recover data sets from fast replication backup versions

Backup function

Backup is the process of copying a data set from a level 0 or an ML1 volume to daily backup volume. This copy is called a backup version. The purpose of backup is to have copies of data sets in case something happens to the original data sets. The difference between dump and backup is that the dump function backs up the entire allocated space on a volume, whereas the DFSMShsm backup function backs up individual data sets.

DFSMShsm can create backup versions of data sets either automatically or by command. DFSMShsm automatically creates backup versions of data sets on specified days beginning at a specified time of day. The data sets must meet eligibility criteria and must be on DFSMShsm-managed volumes that have been designated for automatic backup.

Fast replication function

Fast replication uses volume-level fast replication to create backup versions for sets of storage groups. You can define a set of storage groups through the SMS copy pool construct. The DFSMShsm FRBACKUP command creates a fast replication backup version for each volume in every storage group defined within a copy pool. The fast replication backup versions can be dumped to tape. The dump copies can be created by using the FRBACKUP command or with Automatic Dump processing. You can use FRBACKUP to dump an existing fast replication backup version, or when no backup version exists, create a fast replication backup version and dump it to tape. In all cases, the dump copies are associated with the original source DASD volumes in the copy pool, but not with the target DASD volumes that are actually dumped. The dump time stamps reflect when the fast replication backup version is made, not the actual time of the dumps. Recovery from a fast replication backup version can be performed at the copy pool level from a disk copy, at the individual volume level from a disk or tape copy, or at the data set level from a disk or tape copy. This Fast Replication function enables the backup and recovery of a large set of volumes to occur within a small time frame.

The term fast replication refers to the FlashCopy® function supported by IBM® System Storage® disk and the SnapShot function supported by IBM RAMAC Virtual Array (RVA) disk.

Dump function

Dump is the process of copying all data from a DASD volume to dump tape volumes. Full-volume dump is an extension of DFSMShsm’s availability management that invokes DFSMSdss through the DFSMSdss application interface. Full-volume dump backs up the entire allocated space of DFSMShsm-managed DASD volumes and ML1 volumes either automatically or by command. Non-DFSMShsm-managed volumes are dumped only by command. The purpose of the full-volume dump is to expedite the recovery process when an entire volume is lost or damaged and to supplement the incremental recovery process.

The full-volume-dump process can be one volume in and one dump copy out. It can also be one volume in and multiple dump copies out. Each dump copy is a complete image of the dumped volume, not just an incremental backup of selected data sets. Each successive full-volume dump of a volume, regardless of the number of dump copies, is a generation. Each dump copy in a generation is associated with a different dump class, which specifies how the dump copy is to be managed. DFSMShsm allows from one to five dump copies to be made concurrently for any one full-volume dump. DFSMSdss discontinues writing to dump copies on which errors occur. DFSMSdss creates the multiple copies and continues its full-volume-dump process as long as one output copy is good. DFSMShsm discards the contents of only the bad copies and issues an appropriate message. If all copies fail, the full-volume dump is failed.

DFSMShsm keeps 100 generations of dump copies for any given volume unless all the copies in a generation expire. When all dump copies in any generation for a volume reach their expiration dates, DFSMShsm deletes that generation from its records. When the 100 generations for a particular volume have been reached and the next full-volume dump for that volume is performed, the control records for the oldest generation are discarded, regardless of the retention periods of the individual copies.

Types of backup volumes

You can define the following types of tape or DASD backup volumes to DFSMShsm:

Daily backup volumes: Daily backup volumes are assigned to a specific day in the backup cycle and contain the backup versions created on that day. DFSMShsm creates these backup versions during the backup of a level 0 volume or during the backup of migrated data sets. Daily backup volumes can also contain backup versions created by the BACKDS command. However, the daily backup volume used to contain these manually backed up versions does not necessarily correspond to the day in the backup cycle when DFSMShsm created the backup version. Instead, the daily backup volume corresponds to the day in the backup cycle that DFSMShsm moved the backup version from its temporary location on an ML1 volume to a daily backup volume.
Fast replication target volumes: Fast replication target volumes contain the fast replication backup copies of DFSMShsm-managed volumes. Fast replication target volumes are defined with the SMS copy pool backup storage group type.
Spill backup volumes: Spill backup volumes contain older backup versions of data sets. These backup versions are moved to spill backup volumes when DFSMShsm needs more space on DASD daily backup volumes. Tape spill volumes also receive all valid backup versions of data sets when a tape backup volume is recycled.
Unassigned backup volumes: DFSMShsm uses unassigned volumes whenever it needs more daily or spill backup volumes. There are two types of unassigned volumes: unassigned daily backup volumes and unassigned backup volumes. When DFSMShsm selects an unassigned volume during backup processing, DFSMShsm assigns it as a daily or spill backup volume.
- Unassigned daily backup volumes are those volumes defined to DFSMShsm as daily backup volumes but not associated with any day in the backup cycle. DFSMShsm can use these volumes only as daily backup volumes, but DFSMShsm determines which day in the backup cycle the volume should be assigned to when it first uses the volume.
- Unassigned backup volumes are those volumes defined to DFSMShsm as backup volumes but not specified as daily or spill backup volumes. When it first uses unassigned backup volumes, DFSMShsm assigns the volumes as daily or spill backup volumes. If DFSMShsm uses a volume as a daily backup volume, DFSMShsm determines which day in the backup cycle the volume should be assigned to.
When DFSMShsm needs another daily backup volume, it chooses an unassigned daily backup volume before it chooses an unassigned backup volume.

Recovery and restore of data sets

Recovery and restore are processes that are requested only by command, not automatically, for backed up data sets. Recovery is the process of retrieving a full-volume dump or a backup version of a data set or a volume. Restore signifies that DFSMSdss is used to retrieve dumped data from dump volumes. You can use restore or recover processing to:

Recover a data set that has been lost or damaged.
Recover an earlier version of the data set without deleting the current version.
Restore a volume from a full-volume dump and update the volume from later incremental backup versions.
Restore a data set from a dump copy.
Restore a volume from a full-volume dump.
Recover a volume from DFSMShsm backup versions.
Recover a pool of volumes from the fast replication backup versions on DASD.
Recover a single volume from the fast replication backup versions on DASD or tape.
Recover a data set from the fast replication backup versions on DASD or tape.

DFSMShsm volume recovery can use incremental backups or full-volume dumps or both. One DFSMShsm RECOVER command can be used to request both a volume restore and an incremental volume recovery.

DFSMShsm can recover data sets from a DFSMShsm incremental backup version or from a DFSMShsm dump copy. DFSMShsm automatically chooses the more recent copy of the data set if you allow users to perform data set restores (see Controlling restoring of individual data sets from dump tapes).

There are special considerations for full volume restores of volumes that were dumped using the BACKVOL DUMP command and whose data sets contain RLS attributes.

DFSMShsm support activities

The following topics introduce the activities necessary to maintain DFSMShsm-owned data sets and volumes. In addition to the activities that cause the DFSMShsm program to perform its space management and availability management functions, certain other activities maintain the security and efficiency of DFSMShsm itself. For example, backup copies of the control data sets should be kept, and the DFSMShsm-owned volumes must be maintained.

Maintaining DFSMShsm control data sets, describes the activities necessary to ensure that you can recover from damaged or lost DFSMShsm control data sets.
Managing DFSMShsm media, describes the activities necessary to manage data stored on DFSMShsm-owned volumes.
Obtaining information from DFSMShsm, describes the information that you can obtain from DFSMShsm about its operations and the data sets and volumes that it is managing.
DFSMShsm tape libraries, explains DFSMShsm automated and manual tape libraries.
Using DFSMShsm with DFSMSrmm, explains the interaction between DFSMShsm and DFSMSrmm when managing DFSMShsm tape volumes.
Operating procedures for DFSMShsm, describes procedures to be performed by the computing system operator.
RACF considerations, discusses pertinent RACF® information. RACF is a component of the Security Server for z/OS®. This information includes the use of discrete and generic profiles with DFSMShsm, and the use of FACILITY class profiles with regard to command control access in DFSMShsm.
Health Checker for DFSMShsm, describes information about Health Checker for DFSMShsm.

Data recovery scenarios

Data recovery scenarios, describes real-life examples of data loss and recovery situations. It describes a variety of situations where data is lost, and what steps to take to recover that data. It also includes situations where the lost data is a control data set or journal.