$ZA contains a status determined by the last read on the device. The value is a decimal integer with a meaning determined by the device as follows:
For Terminal I/O:
0Indicating normal termination of a read operation
1: Indicating a parity error
2: Indicating that the terminator sequence was too long
9: Indicating a default for all other errors
For Sequential Disk and Tape Files I/O:
0: Indicating normal termination of a read operation
9: Indicating a failure of a read operation
For Fifos I/O:
Decimal representing $JOB (identifier) of the process that wrote the last message the current process read
$ZA refers to the status of the current device. Therefore, exercise care in sequencing USE commands and references to $ZA.
GT.M does not permit the SET command to modify $ZA.
For more information on $ZA, refer "Input/Output Processing".