The Datacom Interface

Follow the instructions in this topic to allow the QUICKSTART for MVS product to run in a Datacom environment.

  1. Set up the Checkpoint Control Table.
    QUICKSTART uses a DBMS Table to determine whether a Job is Restarting, and if so, from which Checkpoint to Restart. The DBMS Table allows synchronization between the application’s Working Storage (saved in the QUICKSTART Checkpoint Dataset(s)) and the DBMS updates.

    For guidance on installation of this Table, refer to member DCOMDICT in QSTART.SAMPLIB. Ensure that all standard Datacom Table initialization procedures are followed.

  2. SAMGENER Customization
    In order to take full advantage of all of SAMGENER's capabilities, it needs access to the Checkpoint Control Table on your DBMS. Since SAMGENER may be run against multiple DBMS systems at any one site, SAMGENER allows the specification of a DBMS access routine name at run time. This routine will be passed the key to the table. This access routine then performs the read of the DBMS table, returning a return code and a time stamp from the last successful QUICKSTART checkpoint. QSTART.SAMPLIB contains a source code member QSRDDCOM which performs this function. If Datacom is the primary DBMS that QUICKSTART is being installed for, rename this module to QSRDCKPT to avoid having to override the DBMSMOD parameter when running SAMGENER. It must be compiled and linked, AMODE (24) and RMODE (24).

  3. COBOL Customization and Verification
    If COBOL is not being used with Datacom at this installation, this step can be skipped.

    Member DCOMDEMO in QSTART.SAMPLIB contains a sample restartable application program with which QUICKSTART can be tested, the steps are as follows:

    1. Modify the dataset names appearing in the JCL to match those of your installation.
    2. Modify the Table Name, Key Name, and Element Names in the CKPT-RTN Paragraph to match the names of the QUICKSTART Checkpoint Control Table created earlier.
    3. Modify the URT to match the Table Name and Database Names.
    4. Compile, Link, and Run the demo using compile options RES and NODYNAM. The demo copies records in a sequential file from DD name INFILEA to DD name OUTFILED. For DD name INFILEA, select an Input File from your installation that contains at least 30000 records. The program can use any sequential file with its RECFM=FB or RECFM=VB. The IO-Areas are prepared for a maximum LRECL of 5000. While running the demo program, cause an ABEND after several Checkpoints have occurred. An easy test is to add a TIME=(,10) parameter to the Job or Step. This will abend with a S(322). Then, follow the standard restart procedure (see Using) and restart the application.

    Member DCOMCKUP in QSTART.SAMPLIB contains a sample batch application program to inquire and/or update the records of the Checkpoint Control Table defined as a Datacom Table. Compile and Link the program if desired.

    Member DCOMCOB in QSTART.SAMPLIB contains the common code which will be included into every COBOL DATACOM program.

    Member DCOMURT contains a sample URT entry required in every URT that will be using QUICKSTART.

  4. IDEAL Customization and VerificationIf IDEAL is not being used with Datacom at this installation, this topic can be skipped.

    1. Create a URT that contains the Checkpoint Control Table for use by the demo program. Member DCOMURT contains a sample URT entry required in every URT that will be using QUICKSTART.
    2. Import into the IDEAL environment the non-IDEAL subprograms that will be CALLed from IDEAL restartable programs. The source for these programs is in member IDEALSUB of the QSTART.SAMPLIB Library. Note that in the PARM Section of program QUICKSAM, the size of the PARM is 5000 bytes. If necessary, change this to the maximum LRECL expected for sequential file access.
    3. Import and Compile the IDEAL demo program in order to test QUICKSTART. It resides in member IDEALDC of QSTART.SAMPLIB.
    4. Execute the demo program. The demo program copies records in a sequential file from DD name INFILEA to DD name OUTFILED. For DD name INFILEA, select an Input File from your installation that contains at least 30000 records. The demo program can use any sequential file with RECFM=FB or RECFM=VB. The IO-Areas are prepared in this demo program for a maximum LRECL of 5000 bytes. While the demo program is executing, cause an ABEND after several Checkpoints have occurred. An easy test is to add a TIME=(,10) parameter to the Job or Step. This will cause an ABEND S(322). Then, follow the standard restart procedure (see Using) and restart the application.

    Member IDLUPDDC of QSTART.SAMPLIB contains a sample batch application program to inquire and/or update the Records of the Checkpoint Control Table defined as a Datacom Table. Import and compile the program, desired.

    Member IDLONLDC contains an on-line facility to alter the Checkpoint Control Table.

    Member DCOMIDL in QSTART.SAMPLIB contains the common application program source code which will be included into every IDEAL/DATACOM program.


 

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