Product Documentation

FairCom ISAM for C

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Automatic Log Size Adjustment

Long variable-length data records can cause transaction logs to roll over so fast that checkpoints are not properly issued. By default, the FairCom Server automatically adjusts the size of the log files to accommodate long records. As a rule of thumb, if the record length exceeds about one sixth of the individual log size, the size will be proportionately increased. When this occurs, CTSTATUS.FCS receives a message with the approximate new aggregate disk space devoted to the log files.

To disable this adjustment, add FIXED_LOG_SIZE YES to the FairCom Server configuration file. A single-user TRANPROC application can disable the adjustment by setting the global variable ctfixlog to a non-zero value.

Note: When disabled, a record which would have caused an adjustment results in error TLNG_ERR (654) when it is written to a file supporting full transaction processing. It does not apply to pre-image files unless they are part of a dynamic dump with PREIMAGE_DUMP turned on.

ctLOGRECLMT defaults to 96MB in ctclb3.c. If a record exceeds this length and log adjustment is not permitted, the log is not adjusted. An entry is made in CTSTATUS.FCS indicating the approximate record length in megabytes.