6.12.2 Determining the size of the user log files

Any time a database is updated, a user log containing database update history information is stored in a user log file. If a rollback occurs, the HADB server uses the user logs to recover the transaction.

Use the following formula to determine the size of the user log files.

Formula (kilobytes)

Explanation of variables

• user_file_init_size

  Value specified for the adb_log_usrfile_size operand in the server definition

• max_user_log

  Size of the user log for the transaction that outputs the largest volume of user log data (bytes)

When determining the variable max_user_log, first determine the size of the user log for the transactions in each of the processes described below. Then substitute the value of the largest user log size in the variable max_user_log.

• 6.12.3 Determining the size of the user logs that are output during execution of a definition SQL statement (variable max_user_log)

• 6.12.4 Determining the size of the user logs that are output during execution of the adbimport command (variable max_user_log)

• 6.12.5 Determining the size of the user logs that are output during execution of the adbidxrebuild command (variable max_user_log)

• 6.12.6 Determining the size of the user logs that are output during execution of the adbmergechunk command (variable max_user_log)

• 6.12.7 Determining the size of the user logs that are output during database updating (variable max_user_log)

• 6.12.8 Determining the size of the user logs that are output during execution of the TRUNCATE TABLE statement (variable max_user_log)

• 6.12.9 Determining the size of the user logs that are output during execution of the PURGE CHUNK statement (variable max_user_log)

• 6.12.10 Determining the size of the user logs that are output during execution of the adbchgchunkstatus command (variable max_user_log)

• 6.12.11 Determining the size of the user logs that are output during execution of the adbarchivechunk command (variable max_user_log)

• 6.12.12 Determining the size of the user logs that are output during execution of the adbunarchivechunk command (variable max_user_log)

• 6.12.13 Determining the size of the user logs that are output during execution of the adbreorgsystemdata command (variable max_user_log)

• 6.12.14 Determining the size of user logs that are required for the maintenance processing of the updated-row columnizing facility (variable max_user_log)

Tip

User logs are deleted when transaction processing ends. Therefore, calculate the user log file size based on the size of the user log for the transaction that outputs the largest volume of user log data.

Note

For SQL statements and commands not listed above, there is no need to estimate the size of user logs since the user logs that are output are extremely small.

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