X$KCBCBH and X$KCBRBH

Dear firends,

I am not able to see the tuning tables X$KCBCBH and X$KCBRBH having logged in as SYS. Any reason why I am not able to see them? Please help, I am using Oracle 8i.

Hi,
The two tables x$kcbcbh and x$kcbrbh are not in use anymore. They have been discontinued from Oracle 8i.

Regards,
Rohit Nirkhe,Oracle DBA,OCP 8i
[email protected]

i think v$current_bucket ,v$recent_bucket will fulfil ur needs

Ramesh: Unfortunately, I couldn't find even those tables you have mentioned.

ROHIT: Thanks for the info. Then if these tables are discontinued, how do we tune the Database Buffer??

I mean, how do we calculate ACH (Additional Cache Hits) -that would occur for each query and transaction for the buffer increments we make - to tune the Database Buffer??

Kindly help me resolve this question.

Strange, no one to answer this Q :-) Pls help.

yeah ur right as i said those tables are in oracle 8 and those tables are obsolete in 8i. as far as i know to tune the database buffer keep increasing the buffer till u reach the hit ratio. once u wont find any hike in hit ratio that will be the right size for db buffer

[email protected]

From oracle8i the alogrithm for dirty buffer , LRU list , DBWR acitivity has changed for better.
I believe they are forcing us to use multibple buffer pools , then using v$buffer_pool_statistics,
x$bh u can find out which objects are for what pool and then get the statistics from v$buffer_pool_statistics u get the tuning information.

Use STATSPACK. This provides with all the info that was previously provided by X$KCBCBH and X$KCBRBH.

For using V$BUFFER_POOL_STATISTICS u should execute script :
$ORACLE_HOME/rdbms/admin/catperf.sql, because this view is not create by default.

About X$KCBCBH and X$KCBRBH :
some information that was in that tables u can get from new X$ tables:
X$KCBWBPD - buffer pool descriptor and X$KCBWDS.

Quote:

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Originally posted by Shestakov
For using V$BUFFER_POOL_STATISTICS u should execute script :
$ORACLE_HOME/rdbms/admin/catperf.sql, because this view is not create by default.

About X$KCBCBH and X$KCBRBH :
some information that was in that tables u can get from new X$ tables:
X$KCBWBPD - buffer pool descriptor and X$KCBWDS.

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Thanks for the response. Indeed the tables X$KCBWBPD and X$KCBWDS have some info in common.


One more last question:
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With the X$KCBCBH and X$KCBRBH tables -

ACH (Additional Cache Hits) was calculated as
select sum(count) "ACH" from x$kcbrbh where indx < 100;

and

ACM (Additional Cache Misses) was calculated as
select sum(count) "ACM" from x$kcbcbh
where indx >= (select max(indx)+1-100 from x$kcbcbh);



Any idea how do we get these values with the tables X$KCBWBPD and X$KCBWDS.

I would appreciate your answers.

About ACH (Additional Cache Hits) and ACM (Additional Cache Misses) .

THIS IS MY GESS ONLY!!!

When Oracle changed structure and ALGORITHMS of manage db buffer pool this
X$ tables(X$KCBCBH and X$KCBRBH), ACH and ACM has no sense.
When its parameters worked, DB cache had homogeneous structure.
Now (in Oracle 8i, 9i) it has heterogeneous structure with default, keep and recycle areas.
In addition, db buffer has two internal areas "hot" and "cold" blocks and
another algorithm(i named it "middle point", "official" name is Touch-Count).
These are main reasonces, why Oracle excluded X$KCBCBH and X$KCBRBH from dictionary
and why ACH/ACM doesn't work.