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This is part twelve of the series that began with
What is System-Managed Storage?
What is Disaster Recovery?
This article describes disaster recovery using DFSMShsm aggregate backup and recovery support (ABARS). Disaster recovery is a backup and recovery process used to protect against the loss of data in a disaster. The premise is that copies of vital data sets are stored at a location separate from your computer site and that a computer system of approximately the same capabilities is available to resume operations. Since the data must be stored at another site, either it must be on a portable media (tape) or you must automatically transmit it.
Disaster backups are made specifically for recovering data and applications following a disaster. You should not rely on regular backups since disaster backups require special considerations and handling. They are stored off site and are recovered at a remote site. How remote the recovery site is depends upon the type of disaster.
Disaster recovery data should include all data sets critical to your operation, such as critical application data sets, RACF inventory data sets, system data sets, and catalogs.
What Can ABARS Do For Me?
You probably have both critical and non-critical data and applications. The critical ones are those that must run for your business to survive. Non-critical applications can generally wait for recovery until your site has returned to normal operations. When you plan for disaster recovery, consider the types of data, the types of recovery for critical applications, and the recovery sites.
If you have DFSMShsm installed on your system, ABARS is the recommended method for disaster backup and recovery. To use ABARS, you must decide which applications and data sets are critical to your business, and how to transport backup information to the recovery site. Once you have done so, ABARS can assist you in producing a selection data set to be used as input to the ABARS backup function.
Both SMS and DFSMShsm must be active to perform ABARS backup. The data sets to be backed up need not be SMS-managed, but they must be cataloged in an ICF catalog. The ABARS output tapes can be sent to the recovery site by physically moving them, by sending them by the NetView file transfer program or an equivalent product, or by creating tapes remotely in automated tape libraries.
Aggregate Groups
An aggregate group is an SMS construct stored in the SMS configuration.It is a collection of related data sets and control information pooled to meet a defined backup or recovery strategy. Aggregate groups simplify the control of backup and recovery of critical data sets and applications.
The application owner and storage administrator work together to define aggregate groups to enable DFSMShsm to back up and recover groups of data sets that require concurrent action. The data sets are backed up on tape so that copies can be stored at remote sites for disaster recovery. DFSMShsm keeps track of the tapes and can provide you with a list of them when needed. If a disaster occurs, you can use these backups at a remote or local site to recover critical applications.
You can use aggregate groups as a supplement to management class for applications critical to your business. When you define an aggregate group, you can select a management class for it. Backup copies of the aggregate group are managed according to the attributes you define in that management class. This lets you use the same management class for multiple aggregate groups with the same needs without having to define attributes for each aggregate group individually.
Although SMS must be used on the system where the backups are performed, you can recover aggregate groups to systems that are not using SMS, provided the groups do not contain data which requires SMS, such as PDSEs. You can transfer the application's migrated data, along with its active data, without recalling the migrated data.
Tape Storage Groups
A tape storage group definition links a storage group with tape libraries. One tape storage group might be linked to a local tape library, while another might be linked to an off-site tape library. Using it, you can direct disaster recovery tapes to a remote library, and all others to a local library.
Using tape storage groups can help simplify your disaster recovery procedures. Data can be written to tape at an off-site tape library during backup processing and, in the event of a local disaster, rebuilt from those off-site volumes.
Aggregate Backup and Recovery
Aggregate backup and recovery is a process to back up and recover user-defined groups of data sets vital to your business. Aggregate backup can be done by TSO command or in-stream application batch jobs. DFSMShsm uses aggregate groups and management classes to manage the aggregate backup process. Data sets are identified in selection data sets and can be copied, allocated empty, or accompanied on other tapes. ABARS tracks the attributes of the aggregate group, and they can be used to create the proper environment at the recovery site.
Three types of aggregate backup tape files are created: an aggregate control file, an instruction data set, and aggregate data files. The control file contains information needed at the remote site to recover the data sets. The instruction data set is free-form text that contains information to assist in recovering and running the application. The data files contain the data sets you want to recover.
Included in the control file information is the amount of storage required at each hierarchy level to recover the aggregate data sets. This information is generated automatically.
During aggregate recovery, backed-up data sets are recreated at the recovery site. If data set name conflicts arise, a large variety of resolution options are available. They include various forms of rename, replacing the existing data set with the new data set, and bypassing the recovery of certain data sets. There is also a conflict resolution data set that can be edited to handle conflicts. It can be used by aggregate recover processing to resolve conflicts.
Complementary Products
IBM has entered into an agreement with Software Information Services to provide two products which are complementary to ABARS: ABARS Manager and ASAP. ABARS Manager is a user-friendly ISPF panel-based front end which assists the application owner with back up and recovery. ASAP is a product which scans SMF data and job data to determine the data sets which should be included in the ABARS selection data sets.
In Summary
DFSMS/MVS provides the key to system-managed storage in an MVS environment. Using DFSMS/MVS and DFSMShsm’s ABARS, you can develop a disaster backup and recovery strategy. ABARS automatically manages backups of your data sets using the policies you define using aggregate groups and management classes. Unlike DFSMSdss, it can back up user tape data sets, such as DB2 image copies, and it can back up migrated data sets without the need to recall them. In event of a disaster, you can use the recovery capabilities of ABARS to re-establish your critical applications in a timely manner
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