Product Documentation

FairCom ISAM for C

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PAGE_SIZE (sect) optimization

This section applies to all FairCom DB operational models.

The sect argument, the third argument to InitISAM() and the parameter file initialization record, is used to determine the node size (PAGE_SIZE) of the index tree.

Note: If sect is changed, all indexes affected by the change MUST be rebuilt.

Due to the vast number of variables that affect the setting of the sect parameter (key length, number of key values, etc.) it is impossible to provide strict guidelines for setting this value. The best method for setting this value is by performing time trials with various settings on the target platform.

A good “rule of thumb” for determining a starting point for the sect setting is to set the node size of the index to the operating system page size (often referred to as block size).

index node size (in bytes) = sect * 128

Note: The client-side sect setting is ignored by FairCom DB. Instead of relying on the client sect setting, FairCom DB specifies the index node size using the configuration keyword PAGE_SIZE. This keyword accepts the index size in bytes, rather than a multiple of 128 as the sect setting accepts.