System Logger data (SMF 88 records)
System Logger data is processed by the CICS® PA System Logger report. The MVS™ System Logger writes SMF type 88 records to record the System Logger activity of a single system in a sysplex. For capacity planning purposes, we recommend that you view the steady-state performance requirements of an application. Various flags in the SMF type 88 record highlight exception scenarios for additional analysis or changes in report processing.
Record type 88 focuses on the logstream data for a system in a sysplex, including use of interim storage. Interim storage is where log data is initially written, before being written to direct access storage device (DASD) log data sets. You can quickly access data in interim storage without incurring DASD I/O. In a coupling facility logstream, interim storage for log data is in coupling facility list structures. In a DASD-only logstream, interim storage for log data is contained in local storage buffers on the system and duplexed to staging data sets. Using record type 88 can help an installation avoid the STRUCTURE FULL exception, and perform other tuning, capacity planning analysis, or both.
Given a specific logstream, a record type 88 summarizes all of that logstream's activity on that system, as long as at least one address space is connected to the logstream on that system. If no System Logger write activity is performed on the logstream during a particular SMF interval, a record is produced showing zero for the various System Logger activity total fields.
The System Logger SMF record is cut for all logstreams connected at the expiration of the SMF global recording interval. Record type 88 is also triggered by the disconnection of the last logstream on that system.
- Whether the resource is shared sysplex-wide and each system will take action
- Whether the resource is shared sysplex-wide but only one system will take action
- Whether the resource is consumed on a system-local basis
To obtain a sysplex-wide view of System Logger activity, correct processing for most SMF 88 data fields is to sum the field contents for the target interval across all the SMF 88 records produced in the sysplex. There are, however, exceptions to this rule. Because each system must take its own action — that is, wait for an ENF signal indicating that System Logger is available — an analysis program should use the maximum value for these fields: SMF88ERI, SMF88ERC, and SMF88ESF. For example, if a structure rebuild is initiated in a sysplex with three systems, the event is recorded on all three systems. The correct number of structure rebuild initiations is not three, but one or the maximum number provided SMF88ERI.
For DASD-only logstreams, staging data sets are a required part of the logstream configuration. For coupling facility logstreams, use of staging data sets implies a trade-off between performance workload and data integrity. You should try to tune the staging data set size to minimize the number of Staging_Dataset_Threshold_Hit conditions. Without this type of tuning, such conditions can impact performance during staging data set processing. Only an installation can determine what the proper trade-off between performance and data integrity should be.
- For a coupling facility based logstream, the Structure (Interim Storage) section of the record 88 report shows information about the usage of coupling facility structure space allocated for a logstream and the flow of log data through the structure.
- For a DASD-only logstream, the Structure (Interim Storage) section of the record 88 report shows information about usage of staging dataset space and the flow of data through the staging data set for the logstream.
Not all fields in the Structure (Interim Storage) section of the record 88 report apply to DASD-only logstreams. For a DASD-only logstream, fields that do not apply contain zeros. The SMF88STN field contains *DASDONLY* for a DASD-only log stream because there is no structure name.