Granule (Oracle DBMS)

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In computing, a granule is a unit of contiguous (adjacent/bordering) virtual memory allocation.

In the Oracle DBMS, the Oracle server allocates granule entries at the time of instance startup, one for each granule to support the maximum size of the system global area (SGA). During the startup, each component acquires as many granules as it requires. We can say that SGA consists of linked GRANULES. If the SGA size is less than 128 MB, then each GRANULE size will be 4 MB.However if the SGA size is more than 128 MB, then each GRANULE will be 16 MB. At least there must be 3 GRANULES for the SGA: One for Database Buffer Cache, another for Shared Pool Area and one for Redo Log Buffer.