KSDS record length (HISAM)

The database administrator needs to perform trade-offs when determining the KSDS record length for a HISAM database.

Selecting a large KSDS LRECL allows reduction of the number of database records that cannot be stored entirely in the KSDS record. This will reduce the average number of I/Os per database record. On the other hand, selection of a KSDS LRECL that is too large may represent a waste of DASD space, if a high percentage of database record do not fill reasonably the KDSD record.

The table containing the distribution of the database record length (see Figure 1) provides assistance in determining a reasonable KSDS LRECL.

Note: By default, HSSR Engine prints only a table with following ranges of database record length: 1/16, 2/16, 3/16, and so on of the ESDS CI size. These default ranges of database record lengths are seldom sufficient to determine a good KSDS LRECL. To get a table with more appropriate ranges of database record length, provide in the HSSRLDEF data set control statements defining database record length ranges of your choice (for example, database record length ranges of 50 or 100 bytes).