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statistics [message #64692] Sun, 28 December 2003 08:01 Go to next message
ashokmote
Messages: 56
Registered: December 2003
Member
In statistics

wat the meaning of
1.recursive calls ( when it is 0 it means that it is using soft parse.if not it is using hard parse)
2.db block gets (wat it shows)
3.consistent gets( wat the use of it)
4.physical reads
5.redo size(wat it shows ,wat the meaning of that value)

is there any good explanation on this please mention the link.

any tutorial on performance tunning and also sql tunning.
Re: statistics [message #64693 is a reply to message #64692] Sun, 28 December 2003 17:45 Go to previous messageGo to next message
Thiru
Messages: 1089
Registered: May 2002
Senior Member
Recursive calls :
those additional calls(sql) executed by Oracle implicitly to process your (user) sql statement. Can be many things ,not just hard parses. ex) trigger executions , sort extent allocations , data dictionary lookups/updates etc

db block gets :
number of data blocks read in CURRENT mode ie) not in a read consistent fashion, but the current version of the data blocks. DML like Update,Delete will need to access the blocks in the current mode for modification. Most data dictionary calls are done in CURRENT mode.

consistent gets :
number of data blocks accessed in READ CONSISTENT mode. Inorder to maintain statement level read consistency ,Oracle has to read the blocks in a consistent fashion(as of the snapshot SCN) and hence may fetch from rollback segments , which is also added to this statistic.

physical reads :
Physical( disk and/or filesystem page cache) reads. Basically those that cannot be satisfied by the cache and those that are direct reads.

redo size :
Redo ( redo entries are necessary for instance/media recovery : consists of table/index/rollback segment/data dictionary & other changes ) generated in bytes. The redo entries are written out to the online redolog files from the log buffer cache by LGWR.

-Thiru
Re: statistics [message #64694 is a reply to message #64693] Sun, 28 December 2003 18:14 Go to previous messageGo to next message
ashokmote
Messages: 56
Registered: December 2003
Member
thanks ur reply
but in db block gets i could not understand the current mode. how can u known the current mode.how can u see it's current mode value.
Re: statistics [message #64699 is a reply to message #64694] Mon, 29 December 2003 04:25 Go to previous message
Thiru
Messages: 1089
Registered: May 2002
Senior Member
Ashok,
when Oracle fetches the 'current' data blocks(ie as they exist now) to perform Update,Delete,Insert operations,it increments the statistic 'db block gets'. Also when it does a Select that involves recursive sql to access data dictionary, it has to access the 'current' information and hence increments 'db block gets' also.

Oracle knows whether to access in 'consistent' mode or 'current' mode.

These are shown in your sql statistics and also in your system statistics ( v$sysstat)

-Thiru
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