Recovering a CF structure

Conceptually, the data from the previously backed up CF structure is read from the IBM MQ log; the log is read forwards from the backup and any changes are reapplied to the restored structure.

About this task

The log range to use is found from the latest backup of each structure to be recovered, to the current time. The log range is identified by log range sequence number (LRSN) values.

A LRSN uses the six most significant digits of a 'store clock value'.

Note that the whole log (back to the time the structure was created) is read, if you have not done a backup of the structure.

Procedure

1. Check that the logs from each queue manage in the queue sharing group (QSG) are read for records in this LSRN range. Note that the logs are read backwards.
2. Check that a list of changes for each structure to be recovered is built.
3. Data from the coupling facility (CF) structure backup is read and the data is restored. For example, if the backup was done on queue manager A, and the recovery is running on queue manager B, queue manager B reads the logs from queue manager A to restore the structure.

   When the start of the backup of the CF structure is read, an internal task is started to take the restored data for the structure and merge it with the changes read from the log.

4. Check that processing continues for each structure being restored.

Example

In the following example, the command RECOVER CFSTRUCT(APP3) has been issued, and the following messages produced:

04:00:00 CSQE132I CDL2 CSQERRPB Structure recovery started, using log range from LRSN=CC56D01026CC
to LRSN=CC56DC368924
This is the start of reading the logs backwards from each qmgr in the queue sharing group from the time
of failure to the to the structure backup. The LRSN values give the ranges being used.
Log records for all structures (just one structure in this example) being recovered are
processed at the same time.

04:02:00 CSQE133I CDL2 CSQERPLS Structure recovery reading log backwards, LRSN=CC56D0414372
This message is produced periodically to show the process

04:02:22 CSQE134I CDL2 CSQERRPB Structure recovery reading log completed
The above process of replaying the logs backwards has finished,

04:02:22 CSQE130I CDL2 CSQERCF2 Recovery of structure APP3 started, using CDL1 log range
from RBA=000EE86D902E to RBA=000EF5E8E4DC
The task to process the data for APP3 has been started. The last backup of CF structure
APP3 was done on CDL1 within the given RBA range, so this log range has to be read.

04:02:29 CSQE131I CDL2 CSQERCF2 Recovery of structure APP3 completed
The data merge has completed. The structure is recovered.

Parent topic: Example recovery procedures on z/OS