13.1.10 Preventing automatic extension of DB areas
This subsection explains how to prevent automatic extension of DB areas from reducing update processing performance.
If DB area automatic extension occurs when a regular file is used for a data DB area file, dictionary DB area file, or system-table DB area file, performance of update processing during DB area file expansion might deteriorate. Therefore, check whether automatic extension has occurred in the target DB areas.
Check the following item in the information that was output when the adbstat command was executed:
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DBarea_extension_cnt (number of times the DB areas were extended automatically)
- Note
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For details about the adbstat command, see adbstat (Perform Statistical Analysis of the HADB Server) in the manual HADB Command Reference.
If the value that was output to DBarea_extension_cnt is at least 1, DB area automatic extension has occurred. To prevent DB area automatic extension from occurring and causing degradation of update processing, change the data DB area file, dictionary DB area file, or system-table DB area file from a regular file to a block special file. When changing any of these files to a block special file, use one of the methods described in the following to determine the size of the target DB area, and then prepare a block special file with the required size allocated.
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Estimating the size of the target DB area
Determine the size of the data DB area based on the explanation in 5.8 Estimating the size of the data DB area.
Determine the size of the dictionary DB area based on the explanation in 5.11 Estimating the size of the dictionary DB area.
Determine the size of the system-table DB area based on the explanation in 5.12 Estimating the size of the system-table DB area.
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Executing the adbdbstatus command
Determine the usage in the target DB area based on the explanation in Checking the usage of the entire database (output of summary information for DB areas) in Examples under adbdbstatus (Analyze the Database Status) in the manual HADB Command Reference.
After preparing a block special file of the necessary size, change the target DB area file to a block special file. For details about how to change the target DB area file to a block special file, see (1) Changing a data DB area file from a regular file to a block special file in 11.10.5 Changing the storage location of data DB area files.