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DFSFDLG0

DFSFDLG0 is the IMS Physical Logger. Its main function is to write records to the IMS online log data set (OLDS) in an online environment, or the secondary log data set (SLDS) in a batch environment.

DFSFDLG0 is also called for a "check write". This means the caller is waiting for positive confirmation that the log record is physically on DASD. In this case the partially filled OLDS buffer is written to the write-ahead data set (WADS). Later, when the buffer is it will be written to the OLDS.

This module will also be called for open, close, and force end-of-volume processing. In the event of an abnormal termination of the IMS system, it will be called by the ESTAE routine to purge the OLDS buffers.

Hints

For its mainline processing, DFSFDLG0 does not have much overhead. With a large enough blocksize for the OLDS, the physical logger should do much less work than the logical logger.

Please see the Performance Hint section for module DFSFLLG0 for a discussion of how to analyze and improve the performance of log volume.

Reference Sources

More information is available in the IMS SVSOURCE Library Data Set. See your IMS systems programmer.