 | | | Question on RAC user-managed recovery | Question on RAC user-managed recovery 2006-01-19 - By Harish Kalra
Hi Amir,
Inline with Jonathan reply, As per my understnading, Oracle uses Lampport
scheme for SCN implimentation, which has some limitations also. Like if you
have two instance rac1 and rac2 and both instances are in synch with SCN
100.
Now assume two transactions T1 on rac1 and T2 on rac2.
T2 starts later than commit of T1 and less than the time delay defined by
max_commit_propagation_Delay, in this case T2 may not see changes made by T1
and will increase local SCN (which was 100 on rac2) and assign 101 to
transaction T2. T1 will also have 101 SCN in this case.
So it depends upon setting of max_commit_propagation_delay also. Generally
this is set to 7 seconds and resynchronization of instances for SCN happens
as follows:
Iff max_commit_propagation_delay is less than 1 second then log writer send
message to each instance to update SCN after writing to redo log.
If max_commit_poragation_delay is set to default then oracle will resynch on
every three seconds using piggybacking.
Thanks
-Hairsh Kalra
On 1/13/06, Hameed, Amir <Amir.Hameed@(protected)> wrote:
>
> Folks,
> I am running some time-based database instance recovery tests in the lab
> on a three-node RAC environment. The following command was issued from one
> RAC instance while the others were down. I am trying to understand the way
> the change number (change 7286467501233) is being displayed on the first
> line of each of the first three threads below. Why is this number common
> here? After that, this number is distinct in each subsequent archived log
> file. I would appreciate if someone can explain/clarify it for me.
>
> Thank you
> Amir
>
> SQL> recover database until time '2006-01-12:15:20:00' using backup
> controlfile
> ORA-00279 (See ORA-00279.ora-code.com): change 7286467501233 generated at 01/11/2006 14:38:59 needed
> for thread 1
> ORA-00289 (See ORA-00289.ora-code.com): suggestion : /u107/oradata/archives/e52rac/log_1_778.dbf
> ORA-00280 (See ORA-00280.ora-code.com): change 7286467501233 for thread 1 is in sequence #778
>
> Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
>
> ORA-00279 (See ORA-00279.ora-code.com): change 7286467501233 generated at 01/11/2006 14:38:35 needed
> for thread 2
> ORA-00289 (See ORA-00289.ora-code.com): suggestion : /u107/oradata/archives/e52rac/log_2_463.dbf
> ORA-00280 (See ORA-00280.ora-code.com): change 7286467501233 for thread 2 is in sequence #463
>
> Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
>
> ORA-00279 (See ORA-00279.ora-code.com): change 7286467501233 generated at 01/11/2006 14:38:37 needed
> for thread 3
> ORA-00289 (See ORA-00289.ora-code.com): suggestion : /u107/oradata/archives/e52rac/log_3_408.dbf
> ORA-00280 (See ORA-00280.ora-code.com): change 7286467501233 for thread 3 is in sequence #408
>
> Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
>
> Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
>
> ORA-00279 (See ORA-00279.ora-code.com): change 7286467508134 generated at 01/11/2006 14:43:27 needed
> for thread 2
> ORA-00289 (See ORA-00289.ora-code.com): suggestion : /u107/oradata/archives/e52rac/log_2_464.dbf
> ORA-00280 (See ORA-00280.ora-code.com): change 7286467508134 for thread 2 is in sequence #464
> ORA-00278 (See ORA-00278.ora-code.com): log file '/u107/oradata/archives/e52rac/log_2_463.dbf' no
> longer needed for this recovery
> ..
> ..
>
<div>Hi Amir,</div>
<div> </div>
<div>Inline with Jonathan reply, As per my understnading, Oracle uses Lampport
scheme for SCN implimentation, which has some limitations also. Like if you
have two instance rac1 and rac2 and both instances are in synch with SCN
100.
</div>
<div> </div>
<div>Now assume two transactions T1 on rac1 and T2 on rac2.</div>
<div>T2 starts later than commit of T1 and less than the time delay defined by
max_commit_propagation_Delay, in this case T2 may not see changes made by
T1 and will increase local SCN (which was 100 on rac2) and assign 101
to transaction T2. T1 will also have 101 SCN in this case.
</div>
<div> </div>
<div> </div>
<div>So it depends upon setting of max_commit_propagation_delay also. Generally
this is set to 7 seconds and resynchronization of instances for SCN happens as
follows:</div>
<div> </div>
<div>Iff max_commit_propagation_delay is less than 1 second then log writer
send message to each instance to update SCN after writing to redo log.</div>
<div>If max_commit_poragation_delay is set to default then oracle will resynch
on every three seconds using piggybacking.</div>
<div> </div>
<div>Thanks</div>
<div>-Hairsh Kalra</div>
<div> </div>
<div> </div>
<div> </div>
<div><br><br> </div>
<div><span class="gmail_quote">On 1/13/06, <b class="gmail_sendername">Hameed,
Amir</b> <<a href="mailto:Amir.Hameed@(protected)">Amir.Hameed@(protected)</a>
> wrote:</span>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0
.8ex; BORDER-LEFT: #ccc 1px solid">
<p><font face="Comic Sans MS" size="2">Folks,</font> <br><font face="Comic Sans
MS" size="2">I am running some time-based database instance recovery tests in
the lab on a three-node RAC environment. The following command was issued from
one RAC instance while the others were down. I am trying to understand the way
the change number (
</font><font face="Comic Sans MS" size="2">change 7286467501233) is being
displayed on the first line of each of the first three threads below. Why is
this number common here? After that, this number is distinct in each subsequent
archived log file. I would appreciate if someone can explain/clarify it for me.
</font></p>
<p><font face="Comic Sans MS" size="2">Thank you</font> <br><font face="Comic
Sans MS" size="2">Amir</font> </p>
<p><font face="Courier New" size="2">SQL> recover database until time '2006
-01-12:15:20:00' using backup controlfile</font> <br><font face="Courier New"
size="2">ORA-00279 (See ORA-00279.ora-code.com): change 7286467501233 generated at 01/11/2006 14:38:59
needed for thread 1
</font> <br><font face="Courier New" size="2">ORA-00289 (See ORA-00289.ora-code.com): suggestion : /u107
/oradata/archives/e52rac/log_1_778.dbf</font> <br><font face="Courier New" size=
"2">ORA-00280 (See ORA-00280.ora-code.com): change 7286467501233 for thread 1 is in sequence #778
</font> </p>
<p><font face="Courier New" size="2">Specify log: {<RET>=suggested |
filename | AUTO | CANCEL}</font> </p><br>
<p><font face="Courier New" size="2">ORA-00279 (See ORA-00279.ora-code.com): change 7286467501233 generated
at 01/11/2006 14:38:35 needed for thread 2</font> <br><font face="Courier New"
size="2">ORA-00289 (See ORA-00289.ora-code.com): suggestion : /u107/oradata/archives/e52rac/log_2_463.dbf
</font> <br><font face="Courier New" size="2">ORA-00280 (See ORA-00280.ora-code.com): change 7286467501233
for thread 2 is in sequence #463</font> </p>
<p><font face="Courier New" size="2">Specify log: {<RET>=suggested |
filename | AUTO | CANCEL}</font> </p><br>
<p><font face="Courier New" size="2">ORA-00279 (See ORA-00279.ora-code.com): change 7286467501233 generated
at 01/11/2006 14:38:37 needed for thread 3</font> <br><font face="Courier New"
size="2">ORA-00289 (See ORA-00289.ora-code.com): suggestion : /u107/oradata/archives/e52rac/log_3_408.dbf
</font> <br><font face="Courier New" size="2">ORA-00280 (See ORA-00280.ora-code.com): change 7286467501233
for thread 3 is in sequence #408</font> </p>
<p><font face="Courier New" size="2">Specify log: {<RET>=suggested |
filename | AUTO | CANCEL}</font> </p><br>
<p><font face="Courier New" size="2">Specify log: {<RET>=suggested |
filename | AUTO | CANCEL}</font> </p>
<p><font face="Courier New" size="2">ORA-00279 (See ORA-00279.ora-code.com): change 7286467508134 generated
at 01/11/2006 14:43:27 needed for thread 2</font> <br><font face="Courier New"
size="2">ORA-00289 (See ORA-00289.ora-code.com): suggestion : /u107/oradata/archives/e52rac/log_2_464.dbf
</font> <br><font face="Courier New" size="2">ORA-00280 (See ORA-00280.ora-code.com): change 7286467508134
for thread 2 is in sequence #464</font> <br><font face="Courier New" size="2"
>ORA-00278 (See ORA-00278.ora-code.com): log file '/u107/oradata/archives/e52rac/log_2_463.dbf' no longer
needed for this recovery
</font> <br><font face="Comic Sans MS" size="2">..</font> <br><font face="Comic
Sans MS" size="2">..</font> </p></blockquote></div><br>
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