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Database Administrator's Guide

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LOG_SPACE

LOG_SPACE <Megabytes>

This is the number of megabytes of disk space allocated to storing active transaction logs, starting with a minimum of 2. The FairCom DB Server maintains up to 4 active log files, which consume, in the aggregate, up to LOG_SPACE megabytes of disk space. Log files are numbered consecutively starting with 1. The log file names are in the form L0000001.FCS.

For a server with existing transaction logs, If LOG_SPACE is changed and LOG_TEMPLATE is non-zero, the existing log templates will be the wrong size and should be removed. The log template (L0000000.FCT) is only created when the Log # 1 is created, so the transaction log reset procedure should be followed.

V12 Notes

The maximum allowed value for the LOG_SPACE keyword has been increased from 1GB to 4GB-1. This controls the initial size of transaction logs (of 4 logs specifically), so each log can now grow to just under 1GB. Each individual log can now grow up to 4GB if needed, although 3GB is expected to be the largest size, which will be a 1GB normal log size, plus a potential 2GB variable-length record in a transaction. Fewer logs results in less log file churning with high velocity applications leading to faster consistent transaction throughput.

A change in logic allows us to avoid performing a long series of synchronous writes to the transaction log when we start the server in an empty transaction log directory.

This change significantly speeds up server startup on Linux when the file system has write barriers enabled.

Note: When write barriers are disabled on Linux, synchronous writes are much faster than with write barriers enabled, so FairCom highly recommends running with write barriers off and a battery backed power supply on the machine in production systems for best performance.

With this performance improvement, we have been able to increase LOG_SPACE to 1 GB and we have COMPATIBILITY LOG_WRITETHRU on by default.

The defaults in the Server Configuration File (ctsrvr.cfg) have been modified to optimize performance on modern systems.

  • LOG_SPACE has been increased from 120 MB to 1 GB

LOG_SPACE 1 GB

  • PAGE_SIZE has been increase from 8192 to 32768

PAGE_SIZE 32768

Warning: Changing the PAGE_SIZE is a major maintenance task and should be done carefully and with a full reliable backup. Practice on a copy of your data and server folder until you are confident with the results. For procedures, see Adjusting PAGE_SIZE in the Knowledgebase.

Note: A file created with a larger PAGE_SIZE cannot be opened by a server with a smaller PAGE_SIZE.

Default: 1 GB (prior to V12: 120 MB)

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