Which statement is true about the Log Writer process?

Which statement is true about the Log Writer process?

Which statement is true about the Log Writer process?

A.
It writes when it receives a signal from the checkpoint process (CKPT).

B.
It writes concurrently to all members of multiplexed redo log groups.

C.
It writes after the Database Writer process writes dirty buffers to disk.

D.
It writes when a user commits a transaction.

Explanation:
http://docs.oracle.com/cd/B19306_01/server.102/b14220/process.htm (see log writer
process (LGWR))



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Sayed

Sayed

LGWR writes one contiguous portion of the buffer to disk. LGWR writes:
•A commit record when a user process commits a transaction
•Redo log buffers
•Every three seconds
•When the redo log buffer is one-third full
•When a DBWn process writes modified buffers to disk, if necessary

David

David

D as pointed out by Sayed

Maria

Maria

D IS CORRECT.
C is wrong because LGWR writes before the Database Writer process writes dirty buffers to disk.
infact if DBW discovers that some redo records have not been written, it signals LGWR to write the records to disk, and waits for LGWR to complete before writing the data buffers to disk.

MIchael

MIchael

Why is it B wrong, tho? D is perfectly fine, but why not B?

amsunhasav

amsunhasav

Answer is D, there is no concept of multiplexd Redo log groups, only have an option for multiplexing of redo log members. The option B is wrong because, log writer won’t write to multiplexed redo groups(multiple redo log groups) concurrently and writes to multiplexed redo memebrs in the same redo log group concurrently.