12F

Explanation
A program issued an STIMER macro with incorrect
parameters. A reason code in register 15 explains the error: Code
Explanation
00
The system could not find a data area that was specified on a
parameter for an STIMER request.
04
The Coordinated universal time (UTC) or local time of day (LT
or TOD) parameter was specified for a TASK type STIMER request.
0C
The value for the Coordinated universal time (UTC) or local time
of day (LT or TOD) parameter was greater than 24:00:00.00.
10
The STIMER service routine cannot access the storage containing
the user-specified parameters for the STIMER macro.
14
The STIMER service routine received an STIMER macro parameter
that was not valid. For example, a program running in 31-bit addressing
mode is not using the MVS/SP Version 2 or later version of the STIMER
macro.
28
The requested time interval was too large.  One of these situations
occurred: For TASK type requests, the requested MICVL time interval
was larger than X'7FFFFFFFFFFFFFFF'. For REAL/WAIT type requests,
the requested time interval (BINTVL, DINTVL, MICVL, or TUINTVL) added
to the current TOD clock contents would have exceeded X'FFFFFFFFFFFFFFFF' (a
value that would expire on September 17, 2042). A value greater than X'7FFFFFFF' was
specified for BINTVL.

System action
The STIMER routine produces a tailored dump that
provides the following information: The control blocks associated with the task that issued the STIMER
request
The register contents for the task that issued the STIMER request
The virtual subpools that contain the parameter list passed to
STIMER

Programmer response
Depending on the reason code, one of the
following: Code
Explanation
00
Check the spelling of the data area name on the STIMER request.
04
Do not specify the TASK parameter with the GMT and TOD parameters
on the STIMER request.
0C
Change the value for the GMT and/or TOD parameter(s) to one that
is less than 2400.
14
Check that a program running in 31-bit addressing mode uses the MVS/SP Version
2 or later version of the STIMER macro.
10
Change the parameter address so it is in the caller's addressable
storage.
28
Ensure that the specified time interval is correct.

Source
Timer supervision