Queue length ?

[Sofiane]

Hello,

I find the following explanation of Dirty Queue Length & Write Requests :

Dirty Queue Length - Value for dirty queue length
Write Requests - Value for write requests (total)
Write Request Queue Length - Average request queue length

Could you give me more explanations (clear explanation) about the Dirty Queue Length & Write Requests.


Thanks a lot

Sofiane

[gpsingh]

Dirty queue length:

The number of dirty buffers in buffer cache to be cleared by DBWR , should be zero or increase number of DBWR if it is consistently high.

Write requests : Writes by LGWR , if it is high and log file sync is high, tune log_buffer

[Sofiane]

thanks gpsingh

What's about the Average Request Queue Length (How is is interpreted).

Thanks in advance

Sofiane

[rohitsn]

Hi,

Write requests
This statistics stores the number of times DBWR takes a batch
of dirty buffers and writes them to the disk

Dirty Queue Length
After every write request the dirty LRU queue length.
i.e the leftover no of dirty buffers which are waiting to
be written to the disk.


If any doubts,please be free to write to
rohitsn@orasearch.net

regards,
Rohit Nirkhe,Oracle DBA,OCP

[gpsingh]

correction
write requests
This statistic stores the number of times DBWR (not LGWR) takes a batch of dirty buffers and writes them to disk.
But if log_file_sync is high , you have to tune log_buffer

And

SELECT SUM(DECODE(name,'summed dirty queue length',value)) /
SUM(DECODE(name,'write requests',value)) "Write Request Length"
FROM v$sysstat WHERE name IN ( 'summed dirty queue length','write requests')
AND value > 0;

If this value is larger than 1/4(db_block_buffers) increase db_file_simultaneous_writes.

[Sofiane]

Thanks a lot for these information