IMS recovery using Extended Recovery Facility
To operate IMS in an Extended Recovery Facility (XRF) complex, you must understand what tasks to perform during each XRF phase, from initialization through termination.
- Initialization:
- How to bring up the active IMS subsystem
- How and when to bring up the alternate IMS subsystem
- Synchronization:
- Whether or not to enter the
/CHECKPOINT SNAPQcommand
- Whether or not to enter the
- Tracking:
- How to use the
/DISPLAYcommand and read the status line of the master terminal - How to use online change
- How to change surveillance dynamically
- How to use other XRF-related commands
- How to use XRF in an IMS DBCTL environment
- How to use XRF in a data-sharing environment
- How to use the
- Takeover:
- How does automatic takeover differ from manual takeover
- How to work with the operator of the other subsystem and the operator of the network
- How to initiate a takeover
- How to ensure I/O prevention on the failed active subsystem
- When to end I/O toleration on the alternate subsystem
- How to switch DASD and class-3 terminals
- Post-takeover:
- How to ease the workload on the new active subsystem
- How and when to restore service to class-3 and class-2 terminals that failed to switch
- How to complete dynamic DL/I backouts
- How to perform diagnostics on the failed subsystem
- How to bring up a third subsystem as an alternate or to restore the original active as the alternate subsystem
- Termination:
- How to terminate an XRF complex
- How to stop surveillance
XRF requires the following resources:
- z/OS®, IMS, and VTAM®, running on each central processor complex (CPC).
- If USERVAR is used, Network Control Program (NCP) running on a 3725 Communication Controller for full terminal switching.
- IMS system logs— online data sets (OLDSs) and write-ahead data sets (WADSs)—and certain other system data sets must be on DASD shared by both IMS subsystems.