Jonathan,
Clay,
Only a minority of databases is affected by this problem. Other databases
running on the same server and under the same Oracle home are healthy. I
couldn’t find any difference between databases that work and those which don’t.
I discovered that 12.2 is affected too (I originally reported the problem for
18c and 19c)
v$transaction_time.start_date und start_time are constant for every transaction
and every session on an affected database. This value doesn’t change over time.
Consequently these it isn’t function of v$timer.hsecs.
v$transaction_time.start_date is some arbitrary time higher than startup_time,
for example.
select
2 ( select start_date from v$transaction )
3 -
4 ( select startup_time from v$instance )
5 from dual ;
(SELECTSTART_DATEFROMV$TRANSACTION)-(SELECTSTARTUP_TIMEFROMV$INSTANCE)
----------------------------------------------------------------------
70.2931366
V$transaction.start_date is different on each database. Alert.log doesn’t show
any anomalies around this time.
After a database restart start_date gets populated correctly.
Best regards,
Nenad
http://nenadnoveljic.com/blog/
From: oracle-l-bounce@xxxxxxxxxxxxx <oracle-l-bounce@xxxxxxxxxxxxx> On Behalf
Of Clay Jackson (cjackson)
Sent: Dienstag, 1. September 2020 00:11
To: jlewisoracle@xxxxxxxxx; ORACLE-L (oracle-l@xxxxxxxxxxxxx)
<oracle-l@xxxxxxxxxxxxx>
Subject: RE: wrong start_time and start_date in v$transaction
But, didn’t Nenad say “start_time doesn’t change over time on the affected
databases”.
Could it be as simple as the start time of the instance?
But then why SOME transactions and not ALL? Perhaps something as simple as
“the first transaction in each session”?
Clay Jackson
From: oracle-l-bounce@xxxxxxxxxxxxx<mailto:oracle-l-bounce@xxxxxxxxxxxxx>
<oracle-l-bounce@xxxxxxxxxxxxx<mailto:oracle-l-bounce@xxxxxxxxxxxxx>> On Behalf
Of Jonathan Lewis
Sent: Monday, August 31, 2020 2:54 PM
To: ORACLE-L (oracle-l@xxxxxxxxxxxxx<mailto:oracle-l@xxxxxxxxxxxxx>)
<oracle-l@xxxxxxxxxxxxx<mailto:oracle-l@xxxxxxxxxxxxx>>
Subject: Re: wrong start_time and start_date in v$transaction
CAUTION: This email originated from outside of the organization. Do not follow
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Nenad,
How about one "what if" (based on a bug pattern seen in an older version of
Oracle) before doing anything complicated.
What if: the thing creating the timestamp for the transaction is dividing a
counter by the wrong power of 10 before adding seconds to the database startup
time. If you check v$instance.startup_time + v$timer.hsecs/(100 * 86400) at
the start of the transaction that should (I think) be very close to sysdate:
can you get your transaction start time by dividing hsecs by a couple more
powers of 10 ?
Regards
Jonathan Lewis
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