If the WTOEXIT is specified with WTO=WTOEXIT in the PARM parameter of the EXEC statement on the startup JCL, a 3904 abend can be experienced.
IDMS - all supported releases
The 3904 abend will occur if the WTOEXIT load module is being loaded from a PDSE loadlib and there is no SVC= identification in the PARM parameters. For PDSE support, the SVC= clause is mandatory.
See PDSE Support in System Operations Guide