Leveraging Checkpoint Processing - High-Performance Web Databases: Design, Development, and Deployment - page 664

All jobs should be restartable by just submitting them
again. (Of course, you may have to change the JCL to provide the system
with the checkpoint id indicating the correct restart point.)

Recommendation:

• File Allocation: Make sure that all output files have DISP=OLD. This
means that they are exclusively reserved for use by your program. It
also means that you will not attempt to reallocate them during a re-
start. Allocate report files in a different job. The last thing that you
need is to have an important report file deleted and reallocated during
a restart.
• Do not write directly to a +1 version of a Generation Dataset. Once
again, upon restart, a +1 G.D.G. would refer to a different dataset. In-
stead of changing all +1 to +0 just before a restart, I recommend that
you write to a simple sequential file. You can use IEBGENER utility to
back it up to a +1 G.D.G. in a following step after the program has suc-
cessfully completed. There are other approaches that would work just
as well.

APPLYING CHECKPOINT RESTART TO ANY SQL BASED DBMS

You want to use Checkpoint/Restart in all your batch programs. But, you
don't have IMS. Nor do you have a vendor tool. However, you do have an
SQL database management system (DBMS) such as DB2, ORACLE, SYS-
BASE or SQL SERVER. In this case, I propose the following “magic-box” so-
lution. It requires the use of 2 new tables; one to record Save-area data and
a second table to record output file records.

CREATE SAVE_AREA_DATA TABLE
PROGRAM_NAME 8 CHARACTER,

CHECKPOINT_ID 8 CHARACTER,

DATE_CHPT_TAKEN DATE,

TIME_CHPT_TAKEN TIME,

SAVE_FIELD_AREA_ID SMALL INT,

SAVE_FIELD_DATA VARCHAR;

CREATE OUTPUT_FILE_DATA TABLE
PROGRAM_NAME 8 CHARACTER,

FILE_DDNAME 8 CHARACTER,

RECORD_COUNTER INTEGER,

RECORD_DATA 133 CHARACTER;