Analyzing Your Locking Protocol

The XES Accounting and Measurement service, IXLMG, provides information to assist an exploiter of XES locking services in analyzing the efficiency of its locking protocol. The service returns information about a connection's use of a particular structure in an area mapped by the IXLYAMDA macro. The following fields are of interest while doing this analysis:

IXLYAMDSTRL_NLE
This field contains the number of entries allocated in the lock table portion of the lock structure. The value of this field may help the application determine when it is experiencing false contention due to having insufficient lock table entries to accommodate the range of hash values.
IXLYAMDSTRL_REQCT
This field contains the total number of IXLLOCK, IXLRT, and IXLSYNCH requests issued for this lock structure.
IXLYAMDSTRL_NLTEC
This field contains the total number of lock table entries whose composite state is shared or exclusive; that is, a count of lock table entries that currently have resources mapping to them. This field can be used along with the IXLYAMDSTRL_REQCT field to determine how evenly the application's hashing algorithm is distributing the hash values across the allocated lock table entries. This count is only substantially accurate.
IXLYAMDSTRL_REQCTASYNC
This field is a subset of the total request field and contains the number of requests which XES experienced a delay in servicing. The delay can occur for various reasons such as contention or XES not being able to immediately obtain serialization on its own structures. This field can be used in conjunction with the IXLYAMDSTRL_REQCT field to determine the percentage of requests which XES was able to service immediately without delays.
IXLYAMDSTRL_CONTCT
This field is a subset of the IXLYAMDSTRL_REQCTASYNC field and contains the number of requests that were delayed due to contention. Note that this field contains the number of instances of both resource contention and false contention.
IXLYAMDSTRL_FCONTCT
This field is a subset of the IXLYAMDSTRL_CONTCT field and contains the number of requests that were delayed due to false contention. An application can determine the number of requests experiencing resource contention by subtracting this value from the IXLYAMDSTRL_CONTCT field.
IXLYAMDSTRL_MLSEC
This field contains the maximum number of record data elements allocated in the lock structure. This count is only substantially accurate.
IXLYAMDSTRL_CRITICALREQUESTCOUNT
This field contains the total number of IXLLOCK requests specified with CRITICALREQUEST(IxllockCriticalRequestYes). This count is only substantially accurate.

This information may also be obtained by executing the appropriate Resource Measurement Facility™ (RMF™) Coupling Facility Activity reports. See z/OS RMF User's Guidefor additional information about these reports.