6.12 Estimating the size of the system log files

This section explains how to estimate the size of the system log files.

System log files consist of a master log file and a set of user log files. The master log file and user log files are created with their initial size in the DB directory ($DBDIR/ADBSYS/ADBSLG) when the HADB server starts. The master log file is created automatically, and the user log files are created with the value specified in the server definition. Therefore, to determine the size of the system log files, you need to determine the sizes of the master log file and the user log files.

When an increase in the size of the system logs causes a system log file to exceed its initial capacity, the system log file is automatically extended. Because extending a system log file greatly impacts update performance, make sure that you estimate the size of the system log files so that you can specify an initial capacity that will accommodate your needs.

Use the formula shown below to determine the size of the system log files. Because unusable areas might occur in system log files, specify a size that is at least 1.2 times the value determined here.

Formula (kilobytes)

system log file size = MSTLOG + USRLOG × user_file_num

Explanation of variables

• MSTLOG

  Size of the master log file (kilobytes)

  Determine the value as explained in 6.12.1 Determining the size of the master log file.

• USRLOG

  Size of user log files (kilobytes)

  Determine the value as explained in 6.12.2 Determining the size of the user log files.

• user_file_num

  Number of user log files (files)

  Determine the value as explained in 6.12.15 Determining the number of user log files.

Organization of this section

• 6.12.1 Determining the size of the master log file

• 6.12.2 Determining the size of the user log files

• 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)

• 6.12.15 Determining the number of user log files

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