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-- To check the BPHR in DB2, use the following query:
SELECT 
  BP_NAME, 
  DEC((POOL_DATA_L_READS + POOL_INDEX_L_READS) / 
  (POOL_DATA_P_READS + POOL_INDEX_P_READS),5,2) AS BP_HIT_RATIO 
FROM 
  SYSIBMADM.BP_READ_IO 
WHERE 
  (POOL_DATA_P_READS + POOL_INDEX_P_READS) > 0;

If your BPHR is less than 90%, you may need to increase your buffer pool size. Remember, increasing the buffer pool size will consume more memory, so it's essential to strike a balance between memory usage and performance.

Another significant aspect of buffer pool tuning in DB2 is managing the page cleaners. Page cleaners are background processes that write dirty pages from the buffer pool to the disk. By default, DB2 automatically tunes the number of page cleaners based on the system's workload. However, if you notice excessive disk I/O, you may want to increase the number of page cleaners.

Finally, you can also partition your buffer pool to improve performance. Buffer pool partitioning allows you to distribute your buffer pool across multiple physical disks. This can significantly reduce disk I/O and increase the speed of data retrieval.

-- To partition your buffer pool in DB2, use the following command:
ALTER BUFFERPOOL BP1 SIZE 10000 PAGESIZE 4 K AUTOMATIC 
  PARTITION BY RANGE (TABLESPACE TS1, TABLESPACE TS2);