7C6

Explanation
The system encountered an error while processing
the UCBPIN macro with the UNPIN option. A hexadecimal reason code
in register 15 explains the error: Code
Explanation
01
The PTOKEN supplied as input on the UCBPIN macro request contains
incorrect data.
02
The PTOKEN supplied as input on the UCBPIN macro request contains
non-addressable data.

System action
The system abnormally ends the task, unless a
recovery routine was provided to handle the interruption.

Programmer response
Check your programs for one of the following
possible scenarios causing the abend: A task does the following: Pins a unit control block (UCB) without specifying the LASTING
parameter on the UCBPIN macro.
Schedules a service request block (SRB) to unpin the UCB.

 Because the program did not specify LASTING on the UCBPIN macro,
the task ends before the SRB is dispatched. When the task ends, the
system unpins the UCB. When the SRB subsequently tries to unpin the
same UCB, the system issues this abend.
The PTOKEN specified on the UCBPIN macro is overlaid or altered
by the application program.

Source
Input/output supervisor (IOS)