IDMSDB--Overview

What are STAE Exits?

STAE exits (system task abend exits) are user-written recovery modules supported by DC/UCF systems. STAE exits can be invoked in the event of a program interrupt or an abnormal condition encountered by the task. The user-written module can attempt to recover the task by correcting the abnormal condition. If the abnormal condition cannot be resolved, the STAE program can request abnormal termination of the task.

How STAE Exits Work

For each task level, a program can designate a STAE routine by issuing a #STAE request. A task abnormally terminates due to a processing error or an #ABEND command. When a task terminates abnormally, STAE routines for the abended program and for all higher-level programs are executed. #STAE routines can be overridden by a #RETURN statement or excluded explicitly by an #ABEND request from the program that failed.

Note: For more information about how to issue a #STAE request, see "#STAE" in Chapter 7.

STAE routines determine the cause of the abnormal condition or program interrupt by checking the abend control element (ACE). When control is transferred to the STAE routine, DC/UCF automatically sets the value in register 1 to the address of a fullword parameter list that contains the address of the ACE. When program execution is interrupted, DC/UCF saves the contents of all registers from the abended program in the ACE.

Note: #ACEDS is a DSECT provided in the DC/UCF macro library that defines the fields of the ACE. #ACEDS can be copied into the program using the @COPY IDMS #ACEDS statement.

For more information about the abend control element (ACE) DSECT, see the DSECT Reference Guide.

Programming Considerations

Programming considerations for STAE routines are as follows:

STAE programs must be defined at system generation.
Resources held by the task remain intact when the STAE routine is invoked.
STAE routines can issue DC/UCF requests. However, if an error occurs which would normally abort the task, the DC/UCF system will abnormally terminate.
STAE routines must end with a #RETURN statement. The #RETURN statement can request further action to be taken by specifying the TYPE=NORMAL/ABORT/CONTINUE parameter. If TYPE=CONTINUE is specified, the STAE routine must load the address of the instruction from where processing is to continue in the ACE.

Beginning Register Values

At the start of execution of a STAE routine, the DC/UCF system sets registers 1, 13, and 15 to the following values:

Register 1 holds the address of a 1-fullword parameter list that contains the address of the ACE.
Register 13 holds the address of the STAE routine save area if the SAVAREA option has been defined for the STAE program at system generation.
Register 15 holds the entry-point address of the STAE routine.

Displacement- decimal (hex)	Label in #ACEDS DSECT	Contents	Field Size
0(0)	ACEPSW	PSW at the time of the interrupt	8 bytes
8(8)	ACEGPRS	General registers from abended program 0-15	64 bytes
72(48)	ACEFPRS	Floating point registers from the abended program 0-6	32 bytes
112(70)	ACEFLG	ACE flag (see table below)	1 byte
115(73)	ACEABCOD	Abend code set by DC/UCF	4 bytes
120(78)	ACEPGMNM	Name of the abended program	4 bytes
129(81)	ACEEPSW	PSW in EBCDIC form	17 bytes
148(94)	ACEOFFST	Displacement of instruction that failed in the abended program	6 bytes
160(A0)	ACEILC	XA program interrupt length counter	1 byte
161(A1)	ACEINTC	XA interruption code	2 bytes
ACEPSWDA	Data at PSW Start 16 bytes before and after PSW	32 bytes

Value	Meaning	Comments
X'80'	Abort was in user mode	Set by DC/UCF
X'40'	Program check	Set by DC/UCF
X'20'	No message is wanted	Set by STAE routine
X'10'	No SNAP is wanted	Set by STAE routine
X'08'	Abort task immediately	Set by #RETURN,TYPE=ABORT
X'01'	Continue processing at R14 address	Set by #RETURN,TYPE= CONTINUE