VariableTABLE_CACHE_MAX_STORAGE_FRACTION
Introduced Version1.148
Description Sets the fraction of disk space to be used for caching file data used for query functions such as match() and readFile().
Default0.001 (0.1%)
Minimum0.0 (0% (disabled, not recommended))
Maximum0.08 (80%)

The file data used in functions like match() and readFile() is stored on disk for up to 24 hours after initial use in order to speed up the exectuion time for queries. This parameter sets the fraction of disk space on the node that will be used as the cache value for this data.