Alex Schonlinner wrote:
...
>
> I thought that v$buffer_pool_statistics contains upto date information
> about how many physical reads have been done since instance startup and
> how many reads in total have been done.
>
> Now I select from the view and store the values in Excel.
> Then I do a FTS on a quite large table (about 12 GB in size, buffer
> cache only 2 GB), thus I would assume that after this query the
> physical reads and total reads increased by about 12 GB of data.
>
...
>
> But I don't see the data, and I see only a small increase in the
> physical reads, although the hard disk was used to 100% (using glance
> utility), so the query really used the hard disk, it really used a FTS
> and it really did not fit into the buffer cache.
>
> Here is a table which contains the data from v$buffer_pool_statistics
> before (KEEP, RECYCLE, DEFAULT) and 5 minutes after the FTS (KEEP*,
> RECYCLE*, DEFAULT*):
>
...
> NAME DEFAULT DEFAULT*
...
> PHYS_READS 47240215 47241120
> PHYS_WRITES 6538609 6540360
Sum(physical_reads) and sum(physical_writes) on all pools should be the
same as 'physical reads cache' and 'physical writes from cache' system
statistics, respectively. Can you check the statistics
physical reads
physical reads cache
physical reads direct
physical writes
physical writes direct
physical writes from cache
in v$sysstat or v$sesstat? (The numbers in the v$sesstat of course
won't match those in v$buffer_pool_statistics)
Yong Huang
Received on Tue Aug 01 2006 - 09:03:26 CDT
