X Dollors !!!!!!!!

You want a definitive answer eh?? ;)

These views were obsoleted in Oracle8i along with the init.ora parameters db_block_lru_statistics and db_block_lru_extended_statistics.

-amar

p.s. I have no claims to be a GURU mind you :D

Thanks AMAR ( if not GURU , may be PANDIT ),

Well I am trying to find out the Buffer Cache Hit Ratios using
X$KCBRBH table. I queried V$FIXED_TABLE too , I have seen a lot of X Dollors , but not this one.

I do not have any idea about the init.ora parameters , which you are talking about. And How they are related to my question ???

Sorry to Bug you again and your help will be very much appreciated,

Madhu

# X$KCBCBH and X$KCBRBH are accessible only to the SYS user

# They are used for tuning the buffer cache

# They are used along with init.ora parameters, db_block_lru_statistics and db_block_lru_extended_statistics. These parameters became obsolete from Oracle 8.1(as amar rightly opined)

# If you set db_block_lru_statistics to TRUE, statistics gets collected in X$KCBCBH. The number of rows in this table is equal to the number of buffers in your buffer cache. The COUNT gives number of hits caused by that buffer.

# If you set db_block_lru_extended_statistics to a number, which will be the number of buffers you want to add to your buffer cache. Then, by querying X$KCBRBH table you will know how many additional hits you are going to get.

# Setting these parameters will cause performance overhead

VJ

Thanks a bunch VJ,
I understood that these parameters are obsoleted, And in order to test this buffre cache hit performance we ( used to )rely on these two parameters .

My only wish is to get the right statistics on buffer cache, so would u suggest me any better way of getting the stats thru
scripts.

Thanks again for your wonderful explanation,
Madhu

You can get the Buffer cache hit ratio form V$SYSSTAT.

Select Name, Value from V$SYSSTAT where Name in ('db block gets', 'consistent gets', 'physical reads');

Buffer Cache Hit Ratio = (db block gets + consistent gets -physical reads)/ (db block gets + consistent gets)


All the best.