E77

Explanation
The IBM® Generic
Tracker for z/OS® encountered
an error or is issuing this ABEND as a diagnostic aid as requested
via a GTZPRMxx DEBUG statement which matched the parameters of a GTZTRACK
service invocation. 
A hexadecimal reason code in the format ccmmyyyy is
displayed along with the E77 abend code or is returned in register
15.
The fields in the reason code are the following:ccmm
This halfword is for IBM internal
use only.
yyyy
This halfword is the unique reason code.

System programmer response
Contact IBM support
if the unique reason code (yyyy) is not within
the range of X'0000'-X'0FFF '. Unique reason codes within that range
are from a diagnostic aid ABEND triggered by a GTZ DEBUG statement.
The reason code is the value of the REASON parameter of the DEBUG
statement.

Source
IBM Generic Tracker
for z/OS.