Since Oracle9i, youhave more flexibility, since youcan havemultiple block sizes in the
same database. In all versions, the default block size for the database is set using the
DB_BLOCK_SIZE instance initialization parameter.
How do youchoose an appropriate block size for an Oracle database? Oracle defaults
to a block size based on the operating system used, but understanding the implications
of the block size can help youdetermine a more appropriate setting for your workload.
The block size is the minimum amount of data that can be read or written at one time.
In online transaction processing (OLTP) systems, a transaction typically involves a relatively
small, well-defined set of rows, such as the rows used for placing an order for a
set of products for a specific customer. The access to rows in these types of operations
tends to be through indexes, as opposed to through a scan of the entire table. Because
of this, having smaller blocks (4 KB) might be appropriate. Oracle won??™t waste system
resources by transferring larger blocks that contain additional data not required by the
transaction.
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