Catalog Recovery
In z/OS, Catalog Recovery refers to the process of restoring an `Integrated Catalog Facility (ICF)` catalog to a consistent and usable state after it has been corrupted, damaged, or lost. This is critical for maintaining access to `VSAM` and `non-VSAM` datasets managed by `SMS`, as catalogs store vital information about dataset locations, attributes, and access paths.
Key Characteristics
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- Focus on ICF Catalogs: Primarily concerns
Integrated Catalog Facility (ICF)catalogs, which are the standard catalog type in modern z/OS environments, managingVSAMandSMS-managednon-VSAM datasets. - Utilizes IDCAMS: The
IDCAMSutility is the primary tool used for catalog recovery operations, employing commands likeEXPORT,IMPORT,REPRO,DIAGNOSE, andRECOVERto manipulate catalog entries and structures. - Rebuild or Restore: Recovery can involve rebuilding an entire catalog from a backup copy (e.g., using
IMPORT CONNECTorREPRO) or selectively restoring damaged entries within an existing catalog. - Critical for Data Access: A corrupted or unavailable catalog renders all datasets it manages inaccessible, making timely and effective catalog recovery paramount for system and application availability.
- Component of Disaster Recovery: Catalog recovery procedures are a fundamental part of a comprehensive disaster recovery plan for z/OS systems, ensuring business continuity by restoring the metadata required to access application data.
- Consistency is Key: The goal is to restore the catalog to a state that is consistent with the actual datasets on disk, preventing
NOTCATLGD 2(dataset not cataloged) orCATLGD 2(dataset already cataloged) errors.
- Focus on ICF Catalogs: Primarily concerns
Use Cases
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- Disk Subsystem Failure: If the volume containing a master or user catalog becomes unavailable or corrupted due to hardware failure, recovery is necessary to restore access to all datasets managed by that catalog.
- Accidental Deletion or Corruption: An inadvertent
IDCAMS DELETEcommand, a software error, or a system abend might corrupt catalog entries or the catalog structure itself, necessitating a restore from a prior backup. - Logical Inconsistency: If a catalog becomes logically inconsistent (e.g., due to an incomplete update),
IDCAMS DIAGNOSEmight identify issues, leading to a recovery process to repair or rebuild it. - Disaster Recovery Scenarios: In a disaster, catalogs must be restored at the recovery site to enable access to application data and system files, often involving restoring a catalog backup and then connecting it to restored data volumes.
- System Migration or Upgrade: During major system upgrades or migrations, catalogs might be moved or rebuilt, and recovery procedures serve as a fallback in case of issues with the new catalog environment.
Related Concepts
Catalog Recovery is intrinsically linked to VSAM and SMS (Storage Management Subsystem) because catalogs are the central repository for information about these datasets. The IDCAMS utility is the workhorse for all catalog operations, including recovery, while JCL is used to execute IDCAMS jobs. It is a vital component of overall Data Availability and Disaster Recovery strategies, ensuring that critical data remains accessible even after failures. Effective