Executing Recovery-Related Functions


While IMS is running, an IMS system programmer or operator might need to complete tasks to recover the system. These tasks include:

  • "Using DBRC Commands"

  • "Creating a Dump of the Message Queues" on page 420

  • "Recovering the Message Queues" on page 420

  • "Archiving the OLDS" on page 421

  • "Making Databases Recoverable or Nonrecoverable" on page 421

  • "Running Recovery-Related Utilities" on page 421

Using DBRC Commands

You can use the /RMxxxxxx commands to perform the following DBRC functions:

  • Start or stop the DBRC application programming interface (API)

  • Record recovery information in the RECON data set

  • Generate JCL for various IMS utilities and generate user-defined output

  • List general information in the RECON data set

  • Gather specific information from the RECON data set

Recommendation:

Allow operators to use the /RMLIST and /RMGENJCL commands. Restrict the use of /RMCHANGE, /RMDELETE, and /RMNOTIFY commands because they update the RECON data set.


Related Reading: For information about using DBRC commands in a data-sharing environment, see "Supporting Data Sharing" on page 391.

Creating a Dump of the Message Queues

If you want to save the message queues in a non-shared-queues environment, use the /CHECKPOINT SNAPQ command. This command writes a dump of the message queues to the log without terminating the online system.

Recommendation:

Schedule the /CHECKPOINT SNAPQ regularly because it shortens the time required for emergency restart if a problem occurs on the message queue data sets. Consider the following intervals:

  • Whenever the OLDS is switched

  • Once each hour

  • Once each shift

  • Twice each day (midnight and noon)

  • Once each day


For a shared-queues environment, use the /CQCHKPT SHAREDQ command to dump the shared message queues.

Recovering the Message Queues

In a non-shared-queues environment, you can recover the message queues during an IMS restart if the previous shutdown included the DUMPQ or the SNAPQ keyword. Specify the BUILDQ keyword on the /NRESTART or /ERESTART command to restore the messages to the message queue data sets from the IMS log. Specify the FORMAT keyword on the /NRE or /ERE command if you also want to reinitialize the message queue data sets.

In order to use the /NRE BUILDQ command, the system must be shut down using either a /CHECKPOINT DUMPQ or a /CHECKPOINT PURGE command. Before you can issue the /ERE BUILDQ command, you need to issue a /CHECKPOINT SNAPQ command.

Restriction:

If a /NRE BUILDQ or /ERE BUILDQ command fails and you cold start IMS, messages are lost and are not processed.


You can use the IMS Queue Control Facility for z/OS program product (5697-I08) to select messages from the OLDS (or SLDS) and reinsert them into the IMS message queues after an IMS cold start.

Related Reading: For more information, see "IBM IMS Queue Control Facility for z/OS, V2" on page 462.

For a shared-queues environment, CQS automatically rebuilds the message queues if the coupling facility fails. You can also use the SETXCF START, REBUILD command to rebuild the queues manually.

Archiving the OLDS

As mentioned in "Archiving an OLDS" on page 383, you should archive the OLDS to an SLDS at regular intervals. If you are not using automatic archiving, the MTO should use the DBRC GENJCL command at regular intervals to generate the JCL for the Log Archive utility and should run the utility.

Making Databases Recoverable or Nonrecoverable

After you delete recovery-related records from the RECON data set, you can change recoverable full-function databases and DEDBs to nonrecoverable by using the DBRC CHANGE.DB NONRECOV command. You can change nonrecoverable full-function databases and DEDBs to recoverable again by using the DBRC CHANGE.DB RECOVABL command.

Use the DBRC LIST.DB command to display whether a database is recoverable.

Running Recovery-Related Utilities

Depending on your recovery strategy, the MTO might be responsible for running various recovery-related utilities at regular intervals. These could include:

  • Database Image Copy utility

  • Database Image Copy 2 Utility

  • Online Database Image Copy utility

  • Database Change Accumulation utility

The MTO should also run these utilities when a database changes from nonrecoverable to recoverable.

Related Reading: For complete information about these utilities, see IMS Version 9: Utilities Reference: Database and Transaction Manager.



Introduction to IMS. Your Complete Guide to IBM's Information Management System
An Introduction to IMS: Your Complete Guide to IBMs Information Management System
ISBN: 0131856715
EAN: 2147483647
Year: 2003
Pages: 226

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