Variables, Substitution, and Assignment › Vartable Facility › Differences Between Mirrored and Standard Vartables

Differences Between Mirrored and Standard Vartables

A mirrored vartable is a standard vartable, allocated with a scope of AOM. SCOPE=AOM is similar to SCOPE=SYSTEM; any NCL procedure can refer to a SCOPE=AOM vartable, but these vartables are logically separate to SCOPE=SYSTEM. That is, there can be a table with an ID=TAB1 in both SCOPE=AOM and SCOPE=SYSTEM.

Mirrored vartables are distinguished from standard vartables by using the &VARTABLE verb to maintain mirrored vartables. This copy can be read from, added to, and updated by an AOM screening table.

In z/OS, the mirrored copy is maintained in (E)CSA; in VM, it is maintained in your product storage. SYSPARMS AOMMIRST=n sets the maximum amount of storage in kilobytes that can be used by mirrored vartables.