Defining an Output Area

When you code the IXLMG macro, you specify where you want the information placed (with the DATAAREA parameter) and the length of the area (with the DATALEN parameter). If the size of the area is too small to contain the requested measurement data, MVS™ returns as much data as can fit in the area you provided. MVS also sets a reason code (IXLRSNCODEMOREDATA) to indicate that more data is available. The proper size for the data area is returned in the IXLYAMDA header. Note that if you provide a larger area for the requested data, subsequent invocations of IXLMG return the latest information from the coupling facility, which may differ slightly from the original data returned when the area was too small.

Handling the IXLRSNCODEMOREDATA Reason Code
The IXLRSNCODEMOREDATA reason code indicates that the DATAAREA you provided is too small to contain all the requested data. You can reissue the IXLMG macro using the value returned in IXLYAMDAAREA_TLEN (total length of output data area needed to contain all the requested information) as the length of your data area. However, as noted, the IXLMG information returned is a snapshot of the current environment — which might change between one invocation of IXLMG and the next. (For example, additional coupling facilities might have been added or removed from the sysplex, thus changing the number of coupling facility records in the output data area.) You must provide code to handle the IXLRSNCODEMOREDATA reason code in case the length of the record(s) you are requesting ever changes.
Retrieving Information from the Output Data Area
The output data area mapped by IXLYAMDA can contain one or more instances of many different types of records, depending on your IXLMG request. To help you reference each of the record types, the data area contains fields indicating the length of the record type and pointers to the next entry for the same record type. You must use these fields to index through the data area in case the length of the record(s) you are requesting ever changes. Using the DSECT length of a particular record type is not recommended because the length might have been changed since your program was assembled.