JVM elapsed and suspend time

The JVM elapsed and suspend time fields provide an insight into the amount of time that a transaction spends in a Java Virtual Machine (JVM).

Care must be taken when using the JVM elapsed time (owner: DFHTASK, field ID: 253) and JVM suspend time (owner: DFHTASK, field ID: 254) fields in any calculation with other CMF timing fields. This is because of the likelihood of double accounting other CMF timing fields in the performance class record within the JVM time fields. For example, if a Java application program invoked by a transaction issues a read file (non-RLS) request using the Java API for CICS® (JCICS) classes, the file I/O wait time is included in both the file I/O wait time field (owner: DFHFILE, field ID: 063), the transaction suspend time field (owner: DFHTASK, field ID: 014) as well as the JVM suspend time field.

A JVM application will invoke the CICS JVM for a number of reasons not just to invoke the main method of the application. These calls include:

The JVM elapsed and suspend time fields are best evaluated from the overall transaction performance view and their relationship with the transaction response time, transaction dispatch time, and transaction suspend time. The performance class data also includes the amount of processor (CPU) time that a transaction used whilst in a JVM on a CICS J8 mode TCB in the J8CPUT field (owner: DFHTASK, field ID: 260). When a transaction uses a JVM in user key, which runs on a CICS J9 mode TCB, the processor time is recorded in the J9CPUT field (owner: DFHTASK, field ID: 267).

Note: The number of Java API for CICS (JCICS) requests issued by the user task is included in the CICS OO foundation class request count field (owner: DFHCICS, field ID: 025).

In CICS Transaction Server for z/OS® Version 2 Release 1, new monitoring fields were introduced to provide additional insight into the processing of CICS Java (JVM) applications. These new fields are, the JVM init time (owner: DFHTASK, field ID: 273), the JVM reset time (owner: DFHTASK, field ID: 275), and the JVM status information in byte 6 of the TRANFLAG field (owner: DFHTASK, field ID: 164).

Performance List and Summary reports: CICS PA provides Sample Report Forms that show the fields related to a transaction's use of a Java Virtual Machine (JVM):
Sample Form
Report
JVMLST
Performance List report (see Performance List report)
JVMSUM
Performance Summary report (see Performance Summary report)