Re: Does Oracle keep a history of which blocks are/were loaded into the buffer cache?
- From: Charles Schultz <sacrophyte@xxxxxxxxx>
- To: "Bobak, Mark" <Mark.Bobak@xxxxxxxxxxxx>
- Date: Tue, 14 Dec 2010 19:31:31 -0600
Mark,
Yeah, I realized my goof with logminer as soon as I sent it. =) Oh well.
Fortunately, I am not overly worried about the overhead associated with
SQL_TRACE; that is an interesting idea. I am not so sure I could sell that
on a Production database, though. v$segment_stats sounds like the best way
to at least get some idea. As I mentioned to another lister, partitioning is
an option on the table but I really want to justify it first before I
blindly offer it as a solution. *grin* The table is not currently
partitioned, hence my analysis.
Thanks for the ideas.
On Tue, Dec 14, 2010 at 17:31, Bobak, Mark <Mark.Bobak@xxxxxxxxxxxx> wrote:
> Charles,
>
>
>
> I’m pretty sure you’re out of luck. Consider that blocks are loaded from
> disk to satisfy queries, as well as DML, and logminer will have nothing to
> say about that. You can enable SQL_TRACE, and it will capture file#/block#
> data, but at great overhead and expense.
>
>
>
> Oracle just doesn’t track to that level of detail, as far as I know. You
> can look at V$SEGMENT_STATISTICS, to get an idea of which segments have more
> physical I/O happening on them, but no detail about which set of blocks in a
> table were most recently loaded from disk. If the table is partitioned by
> date, and the partitions closely align w/ the level of granularity that you
> require for your analysis, that may allow you to use V$SEGMENT_STATISTICS
> and periodic snapshots to determine if newer data is read from disk more
> recently than old data.
>
>
>
> Just some thoughts….hope that helps,
>
>
>
> -Mark
>
>
>
> *From:* oracle-l-bounce@xxxxxxxxxxxxx [mailto:
> oracle-l-bounce@xxxxxxxxxxxxx] *On Behalf Of *Charles Schultz
> *Sent:* Tuesday, December 14, 2010 5:47 PM
> *To:* ORACLE-L
> *Subject:* Does Oracle keep a history of which blocks are/were loaded into
> the buffer cache?
>
>
>
> Good day,
>
>
>
> I am trying to analyze a given table in an effort to determine how often
> the older records are used compared to the newer records. I know I can go
> against the AWR and determine the age of some statements by searching for a
> date column in the table and grabbing the associated bind variable, but this
> obviously misses any queries that limit data via a join (ie, no bind
> variable). Is there a way to determine when a particular range of datafile
> blocks have been last loaded from disk, or how often? I did some digging in
> x$bh but that has no history (that I know of). In the meantime, I'll start
> up a LogMiner session and scrape all interested ROWIDs, but this is not a
> pretty solution. Maybe the only solution?
>
> --
> Charles Schultz
>
--
Charles Schultz
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