high buffers [message #675094] |
Sat, 09 March 2019 09:51 ![Go to next message Go to next message](/forum/theme/orafaq/images/down.png) |
dba4oracle
Messages: 100 Registered: June 2010
|
Senior Member |
|
|
Hi Guys,
from buffer gets of sql can find amount of buffer cache used by query
(like "buffer gets * blocksize=buffer cache usage" makes sense)
or any query to find buffer cache used by particular sqlid
Thanks
|
|
|
Re: high buffers [message #675095 is a reply to message #675094] |
Sat, 09 March 2019 09:55 ![Go to previous message Go to previous message](/forum/theme/orafaq/images/up.png) ![Go to next message Go to next message](/forum/theme/orafaq/images/down.png) |
John Watson
Messages: 8964 Registered: January 2010 Location: Global Village
|
Senior Member |
|
|
Quote:like "buffer gets * blocksize=buffer cache usage" makes sense What if the query uses one buffer and gets it a zillion times? What if the gets are from a direct read, which doesn't use cache at all?
|
|
|
Re: high buffers [message #675096 is a reply to message #675095] |
Sat, 09 March 2019 10:07 ![Go to previous message Go to previous message](/forum/theme/orafaq/images/up.png) ![Go to next message Go to next message](/forum/theme/orafaq/images/down.png) |
dba4oracle
Messages: 100 Registered: June 2010
|
Senior Member |
|
|
so whats the way of finding how much buffer cache particular sqlid is using
any query like using sysstat etc which can give this details
|
|
|
|
|
|
|
|
Re: high buffers [message #675102 is a reply to message #675100] |
Sat, 09 March 2019 10:25 ![Go to previous message Go to previous message](/forum/theme/orafaq/images/up.png) ![Go to next message Go to next message](/forum/theme/orafaq/images/down.png) |
John Watson
Messages: 8964 Registered: January 2010 Location: Global Village
|
Senior Member |
|
|
I'm no sure that the question has an answer. The buffer cache is shared, it isn't assigned to particular queries. What is important is how much PGA the statement needs and uses. That you can see in v$sql_workarea: the amount needed to run optimally or one-pass.
|
|
|
Re: high buffers [message #675103 is a reply to message #675102] |
Sat, 09 March 2019 10:31 ![Go to previous message Go to previous message](/forum/theme/orafaq/images/up.png) ![Go to next message Go to next message](/forum/theme/orafaq/images/down.png) |
dba4oracle
Messages: 100 Registered: June 2010
|
Senior Member |
|
|
Thanks
ok,
actually if can find buffer cache used by particular sqlid,then i can plan and avoid running not so important at peak load time
which significantly use buffer cache ,as currently db showing high cpu,io
|
|
|
|
Re: high buffers [message #675107 is a reply to message #675104] |
Sat, 09 March 2019 11:07 ![Go to previous message Go to previous message](/forum/theme/orafaq/images/up.png) ![Go to next message Go to next message](/forum/theme/orafaq/images/down.png) |
dba4oracle
Messages: 100 Registered: June 2010
|
Senior Member |
|
|
yes true but if not required query fetching large amount of rows could occupy buffer cache till completion of execution impacting others like wait,or disk reads due to non availability of buffer cache /blocks
|
|
|
|
Re: high buffers [message #675109 is a reply to message #675103] |
Sat, 09 March 2019 11:19 ![Go to previous message Go to previous message](/forum/theme/orafaq/images/up.png) ![Go to next message Go to next message](/forum/theme/orafaq/images/down.png) |
John Watson
Messages: 8964 Registered: January 2010 Location: Global Village
|
Senior Member |
|
|
dba4oracle wrote on Sat, 09 March 2019 16:31Thanks
ok,
actually if can find buffer cache used by particular sqlid,then i can plan and avoid running not so important at peak load time
which significantly use buffer cache ,as currently db showing high cpu,io
Are your users telephoning you to complain about "db showing high cpu,io"? If not, what are they complaining about? You have to focus on a problem. A business problem. Not on some arbitrary figure (specially not a figure that doesn't exist).
|
|
|
Re: high buffers [message #675110 is a reply to message #675107] |
Sat, 09 March 2019 11:20 ![Go to previous message Go to previous message](/forum/theme/orafaq/images/up.png) ![Go to next message Go to next message](/forum/theme/orafaq/images/down.png) |
dba4oracle
Messages: 100 Registered: June 2010
|
Senior Member |
|
|
lets say qry1 run every 1 hr is important to run,qry2 run sometimes and not so important but fetch large data,due to qry2 execution and using buffer cache will qry1 be impacted,if so i can plan to run qry2 different non peak time
|
|
|
|
|
|
|
|