Performance Tuning - Question 028

Which of these statements about processes and the buffer cache is accurate?

A . The ARCH process reads dirty data blocks from the buffer cache and writes them to the archive log destination.

B . The server processes are responsible for reading dirty data blocks from disk.

C . The LGWR process writes dirty data blocks to the redo log.

D. The server processes are responsible for reading blocks of data in or into the buffer cache.

E . The server processes are responsible for writing dirty data blocks back to disk.

Explanation:

Answer D: Server processes look for a data block in the buffer cache. If it is found, we have a hit. If not, the server process will scan for dirty blocks that can be moved out of the cache and be replaced by the block that needs to be read from disk. Once the free block is made available, the server process reads the required block from disk and places it in the free block in the buffer cache. DBWn writes blocks to disk; LGWR writes log buffer entries into the redo log files, and the ARCH process reads the redo log files and writes them to the archived redo log file destinations.