DFSMShsm log data set

The DFSMShsm log data sets provide DFSMShsm with information about events on a particular processing unit and about commands that are entered with the LOG command. The DFSMShsm log records this information in chronological order. However, the SMF and the problem determination aid data sets already record much of the information in the log. If you already are keeping SMF and PDA data and you do not have an ISV product that needs to directly scan the LOGX/LOGY files, or if you do not intend to use the HSMLOG procedure, it is recommended that you do not maintain LOGX/LOGY files. Specify DD DUMMY and use the HOLD LOG command.

	DFSMShsm Log Data Set
	Required: No. Allocated by starter set: Yes, see Starter set example. Data set type: Two physical sequential data sets. Storage guidance: The two physical sequential DFSMShsm log data sets must be on the same volume.

Two physical sequential data sets, known to the starter set as HSMLOGX and HSMLOGY, together make up the DFSMShsm log. DFSMShsm records information in the LOGX data set until the LOGX data set is full. Then DFSMShsm swaps the LOGX data set with the LOGY data set, exchanges the names, and informs the operator that DFSMShsm has swapped the log data sets.

To automatically swap the DFSMShsm log data sets at startup, specify LOGSW=YES on the PROC statement of your DFSMShsm startup procedure. You can also swap the DFSMShsm log data sets with the SWAPLOG command. If you do not want the log data sets to swap at startup, specify LOGSW=NO. To prevent the current log from being overwritten during startup, specify DISP=MOD in the DD statements for the log data sets.

The data set names for LOGX and LOGY are not required to be any particular names, but can be originated by your site. Each log entry is stored as a logical record in the physical sequential log data sets. DFSMShsm begins each log entry record with a log record header that contains the record length, record type, creation time, and creation date. The log entry records include:

Function statistics records (FSR), consisting of statistical data about the functions performed by DFSMShsm. The FSR includes start and stop times for DFSMShsm functions and is updated after each data set that DFSMShsm processes.
Daily statistics records (DSR), containing DFSMShsm processing statistics. The processing statistics are updated every hour (if the data has changed) that DFSMShsm is active during the current day.
Volume statistics records (VSR), consisting of one record for each volume DFSMShsm processes during the current day. The record is updated each hour (if the data has changed) that DFSMShsm is active.
Time, when DFSMShsm receives a data set or volume request and when each request is completed. Each request contains a management work element (MWE).
DFSMShsm error processing description (ERP) and subtask abnormal end data (ESTAI).
Data entered with the LOG command.

For the formats of the FSR, DSR, and VSR records, see z/OS DFSMShsm Diagnosis.

Should a system outage occur that does not close the log, DFSMShsm protects against the loss of the log data by periodically saving the address of the written record.