Oracle OCP 1Z0 053 Q52(DB_ULTRA_SAFE)
52.You have the following requirements in relation to the detection of block corruption for your database
instance:
Check for logical self-consistency of data blocks when modified in memory.
Checksums are calculated before and after the block change.
Checks are performed for the lost writes to the physical standby database.
Which method would help you perform the above checks automatically?
A. Set the DB_SECUREFILE parameter to PERMITTED.
B. Set the DB_ULTRA_SAFE parameter to DATA_ONLY.
C. Set the DB_LOCK_CHECKSUM parameter to TYPICAL.
D. Set the DB_LOST_WRITE_PROTECT parameter to TYPICAL.
Answer: B
DB_ULTRA_SAFE设置为DATA_ONLY有以下影响：
1. DB_BLOCK_CHECKING设置为MEDIUM
https://docs.oracle.com/cd/B28359_01/server.111/b28320/initparams045.htm
All LOW checks are performed, as well as semantic block checking for all non-index-organized table blocks.
2. DB_LOST_WRITE_PROTECT设置为TYPICAL
https://docs.oracle.com/cd/B28359_01/server.111/b28320/initparams058.htm
When the parameter is set to TYPICAL on the primary database, the instance logs buffer cache reads for read-write tablespaces in the redo log, which is necessary for detection of lost writes.
3. DB_BLOCK_CHECKSUM设置为FULL
https://docs.oracle.com/cd/B28359_01/server.111/b28320/initparams046.htm
If set to FULL, DB_BLOCK_CHECKSUM also catches in-memory corruptions and stops them from making it to the disk.
参考：https://docs.oracle.com/cd/B28359_01/server.111/b28320/initparams064.htm
instance:
Check for logical self-consistency of data blocks when modified in memory.
Checksums are calculated before and after the block change.
Checks are performed for the lost writes to the physical standby database.
Which method would help you perform the above checks automatically?
A. Set the DB_SECUREFILE parameter to PERMITTED.
B. Set the DB_ULTRA_SAFE parameter to DATA_ONLY.
C. Set the DB_LOCK_CHECKSUM parameter to TYPICAL.
D. Set the DB_LOST_WRITE_PROTECT parameter to TYPICAL.
Answer: B
DB_ULTRA_SAFE设置为DATA_ONLY有以下影响：
1. DB_BLOCK_CHECKING设置为MEDIUM
https://docs.oracle.com/cd/B28359_01/server.111/b28320/initparams045.htm
All LOW checks are performed, as well as semantic block checking for all non-index-organized table blocks.
2. DB_LOST_WRITE_PROTECT设置为TYPICAL
https://docs.oracle.com/cd/B28359_01/server.111/b28320/initparams058.htm
When the parameter is set to TYPICAL on the primary database, the instance logs buffer cache reads for read-write tablespaces in the redo log, which is necessary for detection of lost writes.
3. DB_BLOCK_CHECKSUM设置为FULL
https://docs.oracle.com/cd/B28359_01/server.111/b28320/initparams046.htm
If set to FULL, DB_BLOCK_CHECKSUM also catches in-memory corruptions and stops them from making it to the disk.
参考：https://docs.oracle.com/cd/B28359_01/server.111/b28320/initparams064.htm
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