DB2 space allocation
Calculate the DB2® space allocations using these assumptions and guidance.
In the following calculations, the following assumptions
apply:
- All data spaces and indexes in CICS® IA use Bufferpool BP0, which is a 4 KB page.
- Number of bytes available in a 4 KB page is 4089.
- You must calculate the PRIQTY for all tables and indexes.
- SECQTY is set to 10% of the PRIQTY. For more information on SECQTY, see the DB2 Administration Guide.
To calculate the PRIQTY for tablespaces and indexes, use the following calculation:
ROWS_PER_PAGE = 4089/ROW_SIZE
FREE_BYTES = 4089/100 * PERCENT_FREE
FREE_ROWS = FREE_BYTES/ROW_SIZE
NUM_OF_4K_PAGES = NUM_ROWS / (ROWS_PER_PAGE – FREE_ROWS)
PRIQTY = 4 * NUM_OF_4K_PAGES
This calculation has the following variables:
- ROW_SIZE
- PERCENT_FREE
- NUM_ROWS
The ROW_SIZE and PERCENT_FREE for each tablespace and the indexes are in the tables provided for each DB2 table. To calculate the number of rows for each tablespace and index, see CICS tables and index: CIUCICS1 and CIUCICSX.
However, until you know how many EXEC CICS statements are used by the applications, it is difficult to estimate the number of rows for a DB2 table.
The DB2 table update jobs, CIUUPDB1, CIUUPDB2, CIUUPDB3,
CIUUPDB4, CIUUPDBN, and CIUAFFLD, include a step
to report on the number of rows in a table. For example:
--Show me the number of rows in the CIU_CICS_DATA table
***INPUT STATEMENT:
SELECT COUNT(*) FROM CIU_CICS_DATA READONLY;
+----------------+
1_| 3037 |
+----------------+
For the CIU_CICS_DATA table use the
row count from the load module scanner jobs CIUJCLTS and CIUJCLTD.
Or run the sample SQL member, CIUSPACE, to report on the row count
for all of the CICS IA tables.
Use the reported values to re-create the table space and index if
required.