flushed to disk. The log records are written to disk less frequently and more log 

records are written each time. Initially, set 

LOGBUFSZ

 to 128 (or 256) 4 KB pages. 

The log buffer area uses space controlled by the 

DBHEAP

 database parameter, so 

consider increasing this parameter also.

Later use the snapshot for applications to check current usage of log spaces by 

transactions as presented in Example 9 36.

Example 9 36   Current usage of log space by applications

$db2 update monitor switches using uow on

$db2 get snapshot for applications on sample | grep "UOW log"

UOW log space used (Bytes)                 = 478

UOW log space used (Bytes)                 = 21324

UOW log space used (Bytes)                 = 110865

Before running the application snapshot, the 

Unit Of Work

 monitor should be 

switched on. At the time the snapshot was issued, only three applications were 

running on the system. The first transaction used 478 bytes of log space, the 

second 21324, and the last used 110865, which is roughly 28 pages more than 

the default log buffer size. The snapshot gives only current values from the 

moment the command was issued. To get more valuable information about the 

usage of log space by transactions, run the snapshot many times.

Example 9 37 shows how to get information about log I/O activity. 

Example 9 37   Checking log I/O activity

db2 reset monitor for database sample

# let the transactions run for a while 

db2 get snapshot for database on sample > db_snap.txt

egrep   i "commit|rollback" db_snap.txt

Commit statements attempted                = 23

Rollback statements attempted              = 2

Internal commits                           = 1

Internal rollbacks                         = 0

Internal rollbacks due to deadlock         = 0

grep "Log pages" db_snap.txt

Log pages read                             = 12

Log pages written                          = 630

Before running the database snapshot, you may have to reset the monitors. The 

values gathered by the snapshot are cumulated since the last monitor reset or 

 Chapter 9. Testing and tuning 

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