- UCB=(reg)
- Supplies the address of the UCB for the volume whose VTOC is to
be tested. The UCB address can be for a captured UCB, or for an actual
UCB above or below the 16 MB line. If your program is in 31-bit mode,
this address must be in 31-bit address; the high order byte is part
of the address.
Recommendation: Code
the address of the UCB parameter as register (2-12). Coding an RX-type
address gives unpredictable results.
The CVAFTST macro accepts the
address of a UCB or UCB copy. Unauthorized programs can get a copy
of the UCB by using the UCBSCAN macro and specifying the COPY, UCBAREA,
CMXTAREA, and DCEAREA keywords. The UCB copy and common extension
copy must be below the 16 MB line and on a word boundary. Data accessed
with DCEAREA can be above the 16 MB line. Refer to z/OS HCD Planningz/OS HCD Planning for
details.
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