Using IMS compatible calls

This section describes how to code IMS compatible calls and structures in a PL/I application program.

For more information, see Using AR/CTL-format checkpoint/restart calls and Using the ASAM services through GSAM replacement.

Entry and return

The entry statement must appear as the first executable statement in the program. When AR/CTL passes control to the application program, it passes the addresses, in the form of pointers, to each of the PCBs. The entry statement must list the pointers to the PCBs—not the PCB names:

ANYNAME: PROCEDURE (CHKPPCB,ASAMPCB1,ASAMPCB2, ...)
         OPTIONS (MAIN);
...
RETURN;
Checkpoint I/O area

The easiest way to define the checkpoint I/O area is as a fixed-length character string and then pass the name of the string to AR/CTL as the call parameter:

DECLARE   1 CHKPAREA,
          2 CHKPID CHAR(8),
          2 CHKPPAD CHAR(4);

You can define the checkpoint I/O area as a major structure, a connected array, or an adjustable character string, and then pass the pointer variable that points to that definition. You can also define the checkpoint I/O area as a minor structure if you use a pointer to the minor structure as the parameter. Do not use a character string with the VARYING attribute. If you use substructures or elements of an array, use the DEFINED or BASED attribute.

ASAM I/O area

The easiest way to define the ASAM I/O area is as a fixed-length character string, and then pass the name of the string to AR/CTL as the call parameter:

DECLARE   1 ASAMAREA,
          2 ASAMFLD1 CHAR(4),
          2 ASAMFLD2 CHAR(16),
          2 ASAMFLD3 CHAR(32);
Checkpoint PCB mask

Define the checkpoint PCB mask as a level 1 declaration:

DECLARE   CHKPPCB_PTR POINTER;
DECLARE 1 CHKPPCB_NAME         BASED (CHKPPCB_PTR),
          2 CHKP_FILL1         CHAR(28),
          2 CHKP_STATUS        CHAR(2),
          2 CHKP_FILL2         CHAR(28);
ASAM PCB mask

Define the ASAM PCB as a level 1 declaration:

DECLARE   ASAMPCB_PTR POINTER;
DECLARE 1 ASAMPCB_NAME         BASED (ASAMPCB_PTR),
          2 ASAMPCB_NAME       CHAR(8),
          2 ASAM_FILL1         CHAR(2),
          2 ASAM_STATUS        CHAR(2),
          2 PROCOPT            CHAR(4),
          2 ASAM_RESERVE1      FIXED BIN(31,0),
          2 ASAM_FILL2         CHAR(8),
          2 LEN_FLDS           FIXED BIN(31,0),
          2 ASAM_FILL3         FIXED BIN(31,0),
          2 RSA                CHAR(8),
          2 UREC_LEN           FIXED BIN(31,0);
Call function codes

Define call function codes with declarations:

DCL  FUNC_XRST  CHAR(4)    INIT('XRST');
DCL  FUNC_CHKP  CHAR(4)    INIT('CHKP');
DCL  FUNC_GU    CHAR(4)    INIT('GU  ');
DCL  FUNC_GN    CHAR(4)    INIT('GN  ');
DCL  FUNC_ISRT  CHAR(4)    INIT('ISRT');
AR/CTL calls

The following shows how to code AR/CTL call:

CALL PLITDLI (parmcount, function, parmlist...);
Call Parameters

The following parameters are valid on the AR/CTL call:

PLITDLI

Required. The name of the AR/CTL module to call for support functions. The module names are identical to those used in IMS for compatibility purposes.

parmcount

Required. The address of a four-byte field that contains the number of parameters in this call, not counting this parameter. This field must be first on all PL/I calls.

function

Required. The address of the area that contains the four-byte function code identifying the type of call.

parmlist

Required. A list of parameters that the application program passes to AR/CTL with the call. AR/CTL calls use the same parameter lists required by IMS. The parameters to include in the list depend on the call function. If the call requires more than one parameter, code them in the order listed.

Define the user areas to save in the checkpoint request or CHKP call as part of a structure. The user area cannot be part of a major structure or a stand-alone value. The length field must be declared as a 31-byte fixed binary field, as shown in the following example:

DCL 1 WORKAREA,
      3 ULENGTH FIXED BIN(31) INIT(500);

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