IBM SC34-7012-01 manual Forward recovery, Recovery point non-RLS mode

each CICS allows all units of work with updates for the data set to complete, and then they write the tie-up records to the forward recovery log and the log of logs, and replies to DFSMSdss.

For BWO backups, it is usually not necessary for the forward recovery utility to process a log from file-open time. Therefore, the tie-up records for all open files are written regularly on the log during activity-keypoint processing, and the time that they are written is recorded. To reduce the number of tie-up records if the activity keypoint frequency is high (such as for some large systems), CICS ensures that there is at least 30 minutes’ separation between sets of tie-ups on the log.

Recovery point (non-RLS mode)

The recovery point is a time that can be converted to a position on a forward recovery log. Recovery of the data set requires only the records that are written after that position. Thus all previous records can be ignored by the forward recovery utility.

The recovery point is stored in the ICF catalog. It is initialized when the first file is opened for update against the data set, and updated during activity-keypoint processing and when the file is closed.

The recovery point is not the time of the current keypoint, as there might still be some uncommitted log records that have not been forced. Instead, it is the time of the start of the last keypoint that wrote a complete set of tie-up records and that completed earlier than the oldest uncommitted write to a forward recovery log.

Note:

1.Only one new recovery point is calculated during an activity keypoint. It is used for all data sets that are open for update and eligible for BWO. Thus a long-running task updating a data set that uses BWO will affect the amount of forward recovery needed for all data sets.

2.If you disable activity keypointing in your system (by specifying the AKPFREQ system initialization parameter as zero), BWO support is seriously affected because, after the file-open operation, no more tie-up records are written and the recovery point is not updated. So, forward recovery of a BWO data set must take place from the time that the data set was first opened for update.

Forward recovery

CICSVR fully supports BWO and the log of logs.

If you do not use CICSVR, ensure that your forward recovery utility is able to:

vRecognize whether a backup was made with BWO or not. The DFSMShsm ARCXTRCT macro can be used to determine this.

vUse the BWO attributes and recovery point in the ICF catalog. It should use the DFSMSdfp IGWABWO callable service to do this. See “An assembler program that calls DFSMS callable services” on page 218 for a sample program.

vRecognize the additional tie-up records on the forward recovery logs and, optionally, recognize tie-up records on the log of logs. These are written so that the forward recovery utility can quickly find the correct position without having to scan the entire forward recovery log.

vRecognize after-images that have already been applied to the data set.

216CICS TS for z/OS 4.1: Recovery and Restart Guide