首先看两个参数的定义：
DB_BLOCK_CHECKSUM
DB_BLOCK_CHECKSUM
determines whether DBWn and the direct loader will calculate a checksum
(a number calculated from all the bytes stored in the block) and store
it in the cache header of every data block when writing it to disk.
Checksums are verified when a block is read-only if this parameter is
true and the last write of the block stored a checksum. In addition, Oracle gives every log block a checksum before writing it to the current log.
If this parameter is set to false, DBWn calculates checksums only for the SYSTEM tablespace, but not for user tablespaces.
Checksums
allow Oracle to detect corruption caused by underlying disks, storage
systems, or I/O systems. Turning on this feature typically causes only
an additional 1% to 2% overhead. Therefore, Oracle Corporation
recommends that you set DB_BLOCK_CHECKSUM to true.
DB_BLOCK_CHECKING
DB_BLOCK_CHECKING
controls whether Oracle performs block checking for data blocks. When
this parameter is set to true, Oracle performs block checking for all
data blocks. When it is set to false, Oracle does not perform. block
checking for blocks in the user tablespaces. However, block checking
for the SYSTEM tablespace is always turned on.
Oracle checks a block by going through the data on the block, making sure it is self-consistent. Block checking can often prevent memory and data corruption. Block checking typically causes 1% to 10% overhead, depending on workload. The more updates or inserts in a workload, the more expensive it is to turn on block checking. You should set DB_BLOCK_CHECKING to true if the performance overhead is acceptable.
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