Determine Granule Size in Oracle

What is a memory granule

When a database instance starts up, the amount of memory allocated is determined by the allocations requested in the parameter file (init file or spfile).  This memory is allocated in units called granules. All memory pool sizes will be allocated in multiples of the granule size.

How is the granule size determined

The granule size is determined based on the amount of memory requested at the instance startup. It is based on the SGA_MAX_SIZE.  If MEMORY_MAX_TARGET is specified, then SGA_MAX_SIZE defaults to MEMORY_MAX_TARGET for the purpose of sizing the granule.  Once set, the granule size does not change for the life of the instance.

The granule sizes at the time of writing, are:

RDBMS	SGA_MAX_SIZE (or memory_max_target)	GRANULE SIZE
9.2	<= 128MB	4MB
	> 128MB	16MB
10.2	<= 1GB	4MB
	> 1GB	16MB
11gR1	<= 1GB	4MB
	>1Gb   <= 4GB	16MB
	>4Gb   <= 16GB	64MB
	>16Gb <= 64GB	256MB
	> 64GB	512MB
11gR2	<= 1Gb	4Mb
	>1Gb   <= 8Gb	16Mb
	>8Gb   <= 16Gb	32Mb
	>16Gb <= 32Gb	64Mb
	>32Gb <= 64Gb	128Mb
	>64Gb <= 128Gb	256Mb
	> 128Gb	512Mb

How to find the Granule size

You can check the granule size that is currently set for your database instance by running the following SQL statement as SYSDBA

select bytes from v$sgainfo where name like 'Granule Size';