CDC Guide for z/OS

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Checkpoint Files

The checkpoint files are VSAM KSDS data sets.

Checkpoint file names are based on the prefix specified in the CHKPT_BASENAME parameter and on the suffix, if specified, in the template to which the CHKPT_FILE_CTL parameter points. These parameters are specified in the CAPTPARM configuration member.

You can run PowerExchange Condense with a single checkpoint file. However, this practice is not advisable because it can compromise future restarts of PowerExchange Condense. Informatica recommends that you use at least nine checkpoint files so that you are likely to have enough checkpoint files from which to reconstruct the CDCT file, if necessary. Specify the number of checkpoint files in the CHKPT_NUM parameter in the CAPTPARM member. The default is 3.

The checkpoint files contain several types of records. The following table describes these records:

Checkpoint Record Type	Description
ERT records	Records that store the registration tags and restart tokens. The restart tokens indicate the point at which PowerExchange Condense starts receiving records from the PowerExchange Logger log files.
DCT records	Records that describe the completed condense files. This information is also stored in the CDCT file. The purpose of this record type is to be able to restore the CDCT file to a consistent point during either a warm start or cold start. This information is periodically purged based on the retention period defined in the COND_CDCT_RET_P parameter in the CAPTPARM member. This parameter is also used to purge records from the CDCT file.
RET records	Compressed records that contain only the source instance, registration tag, condense file name, and retention expiry information and that are used to delete CDCT records that exceed the COND_CDCT_RET_P_retention period. PowerExchange Condense creates RET records based on the number of checkpoint files. For example, if you have nine checkpoint files, the formula is: (2 * 9 ) - 1 = 17 This formula indicates that full uncompressed information is held in the checkpoint file records for the last 17 checkpoints. Information from all earlier checkpoints has been compressed into RET records, which includes a subset of the information.
SRT record	A single record in the checkpoint file that defines system-wide information.

During initialization of the Condense job, PowerExchange Condense takes a new checkpoint and issues the following message, which includes the checkpoint file name and time stamp:

PWX-06136 Checkpoint taken to file=hlq.CHKPTVn time=yy/mm/dd hh:mm:ss

For a warm start, this checkpoint information reflects the results of merging the current registrations from the CCT file with the information from the last checkpoint of the previous run. For a cold start, no data is merged because previous checkpoint files are not available.

PowerExchange Condense takes another checkpoint after each FILESWITCH or SHUTDOWN command.

At each checkpoint, the following PWX-06420 message is issued to display the current restart tokens:

PWX-06420 Condense: Checkpoint done. Sequence=sequence_restart_token Logger=logger_restart_token

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CDC Guide for z/OS

CDC Guide for z/OS

Checkpoint Files

Checkpoint Files