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DFSFLLG0

DFSFLLG0 is the IMS Logical Logger. It processes many functions that involve the IMS log, the most frequent of which is to move a log record formatted by the caller into the current log buffer.

Some of the other functions it can process are:

·   open the log

·    close the log

·    force end-of-volume on the current log

·    write a log record and wait until it is physically on DASD before returning

·    read a record from the log (for backout or restart)

DFSFDLG0, the IMS physical logger, will be invoked to actually process these other functions.

Hints

DFSFLLG0 can use significant CPU. It is used to move all types of records to the IMS log buffers. For each record moved, there are environmental factors to validate and buffer management routines to perform. These routines are not extensive, but when multiplied by the number of log records written they can be significant.

You can take two actions to reduce logging. The first is reduce application checkpoint log records by not taking checkpoints too frequently and by using SYNC calls in a BMP environment rather than CHKP calls. The second is reduce the frequency of IMS system checkpoints. This requires an IMS SYSGEN.

The IMS log reporting program IMSPARS will list the number of IMS log records by type. These numbers should be analyzed periodically to see if any unnecessary log records are being written.

Reference Sources

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