Product Documentation

FairCom ISAM for C

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Data File Extension

When the logical size of the data file reaches the physical size of the data file, the server physically extends the file, updates the physical and logical size values in the file header, and then releases the header lock after locking the data file header.

The amount by which the server extends the file when needed depends on the data file extension size set when creating the file. If you specify 0 for the data file extension size for a transaction controlled (ctTRNLOG) file, the server extends by the following amount:

  • If the data record length is <= 2048, extends by 16384 bytes
  • If the data record length is > 2048 and <= 32768, extends by 32768 bytes
  • If the data record length is > 32768, extends by the data record length.

The degree of data file header contention varies based on the number of clients that are adding to the file at the same time rather than the file size. However, the operations that occur within the header lock should be very fast and each adder can proceed in parallel to perform the remaining operation once the space is acquired.