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How to Use the IMS DATA Step Interface

Fast Path DL/I Database Access


Main Storage Databases (MSDB) and Data Entry Databases (DEDB)

The following two Fast Path database types are supported by the IMS DATA step interface by using a BMP region:

Standard DL/I database calls can be used with a PCB that references an MSDB or DEDB to access database segments. Two additional calls are available:

The IMS DATA step interface supports the FLD and POS calls from a BMP region.


FLD Call

The FLD call is used to verify and to update the contents of one or more fields in an MSDB segment. Individual field verification or change specifications are specified in field search arguments (FSAs). (The format and use of FSAs are described in the IBM publication IMS/ESA: Application Programming: EXEC DLI Commands for CICS and IMS.) FSAs are passed to DL/I in the I/O area. Therefore, in the IMS DATA step interface, the PUT statement is used to format the FSAs in the output buffer and to execute the FLD call.

Like any DL/I call, the FLD call returns a status code. In addition, DL/I returns abnormal status information for each FSA in the call. If a non-blank status code is returned from a FLD call, it might be necessary to examine the contents of the FSA return codes. The DL/I INFILE statement option FSARC= specifies a 200-byte character variable to which the first 200 FSA status code bytes can be returned.

The following example issues a FLD call against an MSDB called INVNTORY:

 ssa1='PRODUCT (PRODUCT = LOCKS     )';
   infile msdbpsb dli call=cfunc dbname=database 
      ssa=ssa1 fsarc=fsa_rc;
   file msdbpsb dli;
   cfunc = 'FLD ';
   database = 'INVNTORY';
   put @1 'QUANTITY  H100*QUANTITY -100*ORDERS +1 ';

The call accesses a segment called PRODUCT containing data on locks. The FLD call performs these functions:

If the QUANTITY field value is not greater than 100 when the FLD call is executed, the return code for the first FSA contains a D. The following statements check for errors in the call and print an appropriate message on the SAS log for this error:

if _error_ then do;
   file log;
   if substr(fsa_rc,1,1) = 'D'
   then put / '*** Quantity of Product Locks Less 
      Than 100 ***';
   put _all_;
   _error_=0;
   end;


POS Call

The POS call is used with a DEDB to perform one of the following:

In an IMS DATA step program, the POS call is issued with a DL/I INPUT statement and a DB PCB. After a POS call is issued, the input buffer is formatted with the requested data as explained in the IBM publication IMS/ESA: Application Programming: EXEC DLI Commands for CICS and IMS.

The SAS statements below execute a POS call for a DEDB called ORDERS:

   retain ssa1 'PRODUCT (PRODUCT = LOCKS     )';
   infile dedbpsb dli call=cfunc dbname=database 
      ssa=ssa1;
   cfunc = 'POS ';
   database = 'ORDERS  ';
   input @3 areaname $char8.
         @11 cycl_cnt $pib4.
         @15 vsam_rba $pib4.;

The call obtains the position of the last inserted ORDRITEM sequential dependent segment for the locks PRODUCT segment.

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