Detecting When a List Structure Is Becoming Full

One way to monitor list structure utilization is to periodically check the fields listed below, which are returned in the answer area by certain successful IXLLIST requests:

LAATOTALCNT, which returns the number of list entries in use in the structure (compare to the value of CONALISTMAXENTRYCOUNT.)
LAATOTALELECNT, which returns the number of data elements in use in the structure (compare to the value of CONALISTMAXELEMENTCOUNT.)
LAALISTCNT, which returns the number of entries or data elements on the list. The value specified for LISTCNTLTYPE on the IXLCONN macro when the list structure was allocated determines whether this field represents a count of list entries or data elements. (This value is also returned in LAAMNL_LISTCNT).
LAAMNSL_EMCCNT, which returns the number of EMCs in use in the structure. (LAANMSLS_EMCCNT also contains this value.)
LAAMNSL_MAXEMCCNT, which returns the approximate maximum number of EMCs in the structure. (LAAMNSLS_MAXEMCCNT also contains this value.)

To determine which IXLLIST requests return this information, see the description of the IXLYLAA data area in z/OS® MVS™ Data Areas in the z/OS Internet library.

Another way to monitor list structure utilization is to issue the IXLMG macro periodically and check the following fields:

IXLYAMDSTRL_MLSELC, which returns the approximate maximum number of data elements allowed in the structure
IXLYAMDSTRL_MLSEC, which returns the approximate maximum number of list entries allowed in the structure
IXLYAMDSTRL_LSELC, which returns the number of data elements in use in the structure
IXLYAMDSTRL_LSEC, which returns the number of list entries in use in the structure.

For a keyed list structure allocated in a coupling facility of CFLEVEL=3 or higher, you can also check these additional fields:

IXLYAMDSTRL_EMCCNT, which returns the number of EMCs in use in the structure.
IXLYAMDSTRL_MAXEMCCNT, which returns the approximate maximum number of EMCs in the structure.

These values can be used to calculate the structure's percentage fullness in terms of entries, elements, and EMCs.