Performance Engineering Interview Questions #7

Following are the Performance Engineering Interview Questions Set #7.

Q. 31 What is Redo Size?

Ans: In AWR, Redo size indicates the amount of DML (Data Manipulation Language) activity i.e. insert, update or delete operations that occurred in the database during the specific period.

Performance Engineering Interview Questions #7 - Redo Size

Q. 32 What is the ‘Log Buffer’?

Ans: The Log Buffer caches the redo operation entries, i.e. insert, update, or delete, before writing to disk: the more DML operations, the more entries and the larger the log buffer.

Q. 33 How does (Redo) Log Buffer size impact the performance?

Ans: If the (redo) log buffer size is too small, processes may wait for space, leading to ‘log buffer space’ waits. The proper sizing reduces such waits and improves transaction throughput.

Q. 34 What is the default Oracle redo log buffer size?

Ans: 512 bytes

Note: The default value/size of the log buffer is four times the DB_BLOCK_SIZE, but it is often desirable to set this value higher, particularly if there are many or long transactions generating high rates of the redo log generation.

Q. 35 What is Multiplexing Redo Log Files?

Ans: To protect against a failure involving the redo log, the Oracle Database allows a multiplexed redo log, meaning that two or more identical copies of the redo log can be automatically maintained in separate locations.