DL/I calls for IMS TM system services

The calls are listed in alphabetical order. Each call description contains:

• A syntax diagram
• A definition for each parameter that can be used in the call
• Details on how to use the call in your application program
• Restrictions on the use of the call

Each parameter is described as an input or output parameter. Input refers to input to IMS from the application program. Output refers to output from IMS to the application program.

System service calls must refer only to TP PCBs. The system service calls are described only as they pertain to IMS TM functions.

Syntax diagrams for these calls begin with the function parameter. The call, the call interface, (xxxTDLI), and parmcount (if it is required) are not included in the following syntax diagrams. See specific information for assembler language, COBOL, Pascal, and PL/I in the topic "Defining Application Program Elements" in IMS Version 15.2 Application Programming for the complete structure.

System Service Call Summary

The following table is a summary of which system service calls you can use in each type of IMS TM application program, and the parameters for each call. The following table lists the function code, its meaning, use, parameters, and in which regions it is valid. Optional parameters are shown in brackets ([ ]).

System service calls issued in a DCCTL environment must refer only to I/O PCBs or GSAM database PCBs. Calls that cannot be used in a DCCTL environment are noted.

Language-dependent parameters are not shown here. For language-specific information, see the topic "Formatting DL/I Calls for Language Interfaces" in IMS Version 15.2 Application Programming.

For information on writing calls with programming language interfaces see the topic "Defining Application Program Elements" in IMS Version 15.2 Application Programming.

Table 1. Summary of system service calls

Function Code	Meaning and Use	Options	Parameters	Valid for
APSB	Allocate PSB. Allocates a PSB for use in CPI-C driven application programs.	None	function, aib	MPP
CHKP (Basic)	Basic checkpoint. For recovery purposes.	None	function, i/o pcb or aib, i/o area	batch, BMP, MPP
CHKP (Symbolic)	Symbolic checkpoint. For recovery purposes.	Can specify seven program areas to be saved.	function, i/o pcb or aib, i/o area length, i/o area[, area length, area]	batch, BMP
DPSB	Deallocate PSB. Frees a PSB in use by a CPI-C driven application program.	None	function, aib	MPP
GMSG	Retrieve a message from the AO exit routine.	Can wait for an AOI message when none is available.	function, aib, i/o area	DB/DC and DCCTL(BMP, MPP, IFP), DB/DC and DBCTL(DRA thread), DBCTL(BMP non-message driven)
GSCD 1	Get the address of the system contents directory.	None	function, i/o pcb or aib, i/o area	batch
ICMD	Issue an IMS command and retrieve the first command response segment.	None	function, aib, i/o area	DB/DC and DCCTL(BMP, MPP, IFP), DB/DC and DBCTL(DRA thread), DBCTL(BMP non-message driven)
INIT	Application receives data availability status codes.	Checks each PCB for data availability.	function, i/o pcb or aib, i/o area	batch, BMP, MPP, IFP
INQY	Inquiry. Retrieves information about output destinations, session status, execution environment, and the PCB address.	None	function, aib, i/o area	batch, BMP, MPP, IFP
LOGb	Log. Write a message to the system log.	None	function, i/o pcb or aib, i/o area	batch, BMP, MPP, IFP
RCMD	Retrieve the second and subsequent command response segments resulting from an ICMD call.	None	function, aib, i/o area	DB/DC and DCCTL(BMP, MPP, IFP), DB/DC and DBCTL(DRA thread), DBCTL(BMP non-message driven)
ROLB	Rollback. Backs out messages sent by the application program.	Call returns last message to i/o area.	function, i/o pcb or aib[, i/o area]	batch, BMP, MPP, IFP
ROLL	Roll. Backs out output messages and terminates the conversation.	None	function	batch, BMP, MPP
ROLS	Returns message queue positions to sync points set by the SETS or SETU call.	Issues call with i/o PCB or aib	function, i/o pcb or aib i/o area, token	batch, BMP, MPP, IFP
SETS	Sets intermediate sync (backout) points.	Cancels all existing backout points. Can establish up to 9 backout points.	function, i/o pcb or aib, i/o area, token	batch, BMP, MPP, IFP
SETU	Sets intermediate sync (backout) points.	Cancels all existing backout points. Can establish up to 9 backout points.	function, i/o pcb or aib, i/o area, token	batch, BMP, MPP, IFP
SYNC	Synchronization	Request commit point processing.	function, i/o pcb or aib	BMP
XRST	Restart. Works with symbolic CHKP to restart application program failure.	Can specify up to 7 areas to be saved.	function, i/o pcb or aib, i/o area length, i/o area[, area length, area]	batch, BMP
Note: GSCD is a Product-sensitive Programming Interface.

Related reading: DCCTL users can issue calls using GSAM database PCBs. GSAM databases are described in IMS Version 15.2 Application Programming.