10.8.5 Larger DB2 page sizes and database persistence

WebSphere supports 4 KB, 8 KB, 16 KB, and 32 KB page sizes, and can have larger varchar for bit data columns of about 7 KB, 15 KB, or 31 KB. Using this performance feature, we see faster persistence for HttpSession of sizes of 7 KB to 31 KB in the single-row case, or attribute sizes of 4 KB to 31 KB in the multi-row case.

Enabling this feature involves dropping any existing table created with a 4 KB buffer pool and tablespace. This also applies if you subsequently change between 4 KB, 8 KB, 16 KB, or 32 KB.

To use a page size other than the default 4 KB...

1.	If the SESSIONS table already exists, drop it from the DB2 database:

DB2 connect to session

DB2 drop table sessions

2.	Create a new DB2 buffer pool and tablespace, specifying the same page size (8 KB, 16 KB, or 32 KB) for both, and assign the new buffer pool to this tablespace. Example 10-8 shows simple steps for creating an 8 KB page.

Example 10-8 Creating an 8K page size

DB2 connect to session
DB2 CREATE BUFFERPOOL sessionBP SIZE 1000 PAGESIZE 8K
DB2 connect reset
DB2 connect to session
DB2 CREATE TABLESPACE sessionTS PAGESIZE 8K MANAGED BY SYSTEM USING ('D:\DB2\NODE0000\SQL00005\sessionTS.0') BUFFERPOOL sessionBP
DB2 connect reset

Refer to the DB2 product documentation for details.

3.	Configure the correct tablespace name and page size, DB2 row size, in the session management database configuration.

Restart WebSphere. On startup, the session manager creates a new SESSIONS table based on the page size and tablespace name specified.