Performance Tuning for Content Manager

196 Performance Tuning for Content Manager

Example 8-12 Load command

LOAD FROM /lsdb/sms/exportICMUT01016001.ixf of ixf messages

/lsdb/sms/load_msgICMUT01016001.msg REPLACE INTO ICMADMIN.ICMUT01016001

CHECK PENDING CASCADE DEFERRED ;

After loading the data, run the runstats command to update the catalog

statistics, then run the rebind command.

8.5 Buffer pool tuning

A buffer pool is memory that is used to cache table and index data pages as they

are being read from disk or being modified. The buffer pool improves database

system performance by enabling data to be accessed from memory instead of

from disk. Because memory access is much faster than disk access, the less

often the database manager needs to read from or write to a disk, the better the

performance. Because most data manipulation takes place in buffer pools,

configuring buffer pools is the single most important tuning area. Only large

objects and long field data are not manipulated in a buffer pool.

All buffer pools reside in the Database Global Memory, which is available to all

applications using the database. All buffer pools are allocated when the first

application connects to the database, or when the database is explicitly activated

using the

activate database

command. Use the

activate database

command to

keep the buffer pools primed even if all of the connections terminate. This will be

useful when the connection load is highly dynamic (for example, Web servers).

As an application requests data from the database, pages containing the data

are transferred to one of the buffer pools from disk. The next time an application

requests data, the buffer pool is checked first to see whether the data is in the

memory area; if it is found, there is no need to read data from the disk. Avoiding

data retrieval from disk storage results in faster performance. If the buffer pools

are not large enough to keep the required data in memory, data must be read

from disk. Pages are not written back to the disk until the page is changed, or one

of the following occurs:

 All applications disconnect from the database.

 The database is explicitly deactivated.

 The database quiesces (that is, all connected applications have committed).

Attention: The buffer pool is probably the single most important database

tuning area for DB2.