Home » Oracle » 1z0-052 v.2 » Why is the value set to 4194304 and not to 2516582?
You have executed this command to change the size of the database buffer cache:
SQL> ALTER SYSTEM SET DB_CACHE_SIZE=2516582;
System altered.
To verify the change in size, you executed this command:
Why is the value set to 4194304 and not to 2516582?
A. Because 4194304 is the granule size
B. Because 4194304 is the standard block size
C. Because 4194304 is the largest nonstandard block size defined in the database
D. Because 4194304 is the total size of data already available in the database buffer cache
Correct Answer: A
Explanation/Reference:
Regardless of whether you are using automatic or manual memory management, you’ll find that memory is allocated to the various pools in the SGA in units called granules. A single granule is an area of memory of 4MB, 8MB, or 16MB in size. The granule is the smallest unit of allocation, so if you ask for a lava pool of 5MB and your granule size is 4MB. Oracle will actually allocate 8MB to the lava pool (8 being the smallest number greater than or equal to 5 that is a multiple of the granule size of 4). The size of a granule is determined by the size of your SGA (this sounds recursive to a degree, as the size of the SGA is dependent on the granule size). Vim can view the granule sizes used for each pool by querying V$SGA_DYNAMIC_COMPONENTS. In fact, we can use this view to see how the total SGA size might affect the size of the granules:
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