Re: redo_size values in v$sysstat

Glenn,

The buffer cache hit ratio is meaning less, not only after startup but any time you calculate it. I am pretty sure that I am not the first one and probably not the last one saying that on this mailing list.

Now about the claim of why you need to wait until 10i to get this fixed, has probably something to do with the fact of how the SGA is allocated on the HP platform. Any change in the layout of the fixed SGA will mean a recompile of the code on HP.

Now it looks to me that the upper 4 bytes of the 8 bytes have been set to -1: 18446744069434437169
FFFFFFFF012EEE31
18446744052688746229
FFFFFFFB1B0FF6F5 So you probably could adjust for that ....

Anjo.

Glenn Travis wrote:

> I sent a message last week regarding our values in the v$sysstat table being WAY too large;
> physical_reads = 18,446,744,069,434,437,169
> db_block_gets, physical_reads_direct, physical_writes_direct also.
>
> This prevents us from running the db cache hit ratio queries.
>
> I logged a tar with Oracle and they said it was a bug (#1713403). It is caused by an overflow in v$sysstat when the amount of generated redo grows over 2GB. They say this bug can't be fixed (at least not until 10i!). I am running on 8.1.7 (HP-UX11).
>
> If you are on 8i, could you query the v$sysstat table and let me know if anyone else is seeing this problem?
>
> col name for a20
> col value for 999,999,999,999,999,999,999
> select name,value from v$sysstat
> where name in ('redo size', 'physical reads', 'db block gets')
> /
> NAME VALUE
> -------------------- ----------------------------
> db block gets 18,446,743,996,920,309,855
> physical reads 18,446,744,052,688,746,229
> redo size 17,049,609,736
>
> I find it unacceptable that Oracle would ignore this until 10i. The only time I can get a cache hit ratio is when I first start up the database (which doesn't mean anything). I know hit ratios are overrated and we look at waits more for performance tuning (read all the articles), but it is still frustrating nonetheless.
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Anjo Kolk
  INET: anjo_at_oraperf.com

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