| Definition between 2 metrics "Physical Reads" [message #532188] |
Mon, 21 November 2011 04:58  |
nikko
Messages: 9
Registered: September 2010
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Junior Member |
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Hello
On 10gR2, I cannot find the exact definition of the 2 following metrics :
"Physical Read Total Bytes Per Sec"
and
"Physical Read Bytes Per Sec"
I would want to know what is the difference between them.
PS : i did not find anything in the doc.
Thanks in advance
nikko
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| Re: Definition between 2 metrics "Physical Reads" [message #532201 is a reply to message #532191] |
Mon, 21 November 2011 06:06  |
nikko
Messages: 9
Registered: September 2010
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Junior Member |
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Sorry,
I want to extract some metrics from the awr view dba_hist_sysmetric_summary.
Two of these metrics are "Physical Read Total Bytes Per Sec" and "Physical Read Bytes Per Sec".
And i was unable to find in what they differ by sense.
Regards
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| Re: Definition between 2 metrics "Physical Reads" [message #532208 is a reply to message #532201] |
Mon, 21 November 2011 06:22 |
John Watson
Messages: 8960
Registered: January 2010
Location: Global Village
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Senior Member |
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Hi, Nikko - I've run a few queries, and I think the discrepency may be to do with whether the statistic is accumulated across all sessions or refers only to sessions logged in at any one moment. There also appears to be a difference between reads done by session server processes and by background processes. For instance:
orcl> select * from v$sysstat where lower(name) like '%physical read%bytes';
STATISTIC# NAME CLASS VALUE STAT_ID
---------- ---------------------------------------------------------------- ---------- ---------- ----------
50 physical read total bytes 8 310821888 2572010804
80 physical read bytes 8 149577728 523531786
orcl> select username,sum(value) from v$sesstat natural join v$session
2 where statistic#=50 group by username;
USERNAME SUM(VALUE)
------------------------------ ----------
61323776
JON 70172672
SYS 28498944
orcl> select username,sum(value) from v$sesstat natural join v$session
2 where statistic#=80 group by username;
USERNAME SUM(VALUE)
------------------------------ ----------
35127296
JON 70172672
SYS 8388608
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