What is IMS DEDB Fast Recovery?

In the event an emergency restart fails or, in an extended recovery facility (XRF) complex, when both the takeover by the alternate IMS system and the emergency restart fail, IMS DEDB Fast Recovery can be used to recover data entry databases before the IMS cold start.

IMS DEDB Fast Recovery:
  • Corrects the online log data set (OLDS) by invalidating the logging for transactions that did not reach the sync point, reconstructing the log records (not yet written to the OLDS) from the write ahead data set (WADS), and correctly closing the OLDS, including appropriate updates in the DBRC RECON data sets.
  • Recovers the DEDB areas, except for non-recoverable DEDBs, that were active when IMS failed.
  • Provides procedures and reports to assist system administrators in the processes required before and after IMS cold start.
  • In the two-phase commit process environment such as DBCTL, if IMS abnormally terminates without determining whether the transactions started by another transaction manager are in commit status or in abort status, IMS DEDB Fast Recovery provides a method for resolving the in-doubt status.
    Note: In this information, the word transaction means unit of recovery (UOR) of IMS.
  • To recover block-level data-sharing VSO areas, IMS DEDB Fast Recovery casts out CIs and normally disconnects from Coupling Facility (CF) structures (the Single Area Structures (SAS) or the Multi-Area Structures (MAS)) for the areas that are in use in the failed IMS as well as the typical recovery of CIs.

IMS DEDB Fast Recovery provides an option to perform recovery without using the IMS Database Recovery Control (DBRC) function.

Whenever possible, IMS must be restarted using a normal restart or an emergency restart.

In this information, an IMS cold start with the /ERE COLDSYS command is assumed after the database recovery through IMS DEDB Fast Recovery. But you can perform the IMS emergency restart with the /ERE COLDBASE command instead of the /ERE COLDSYS command. However, IMS emergency restart requires you to do some additional operations.