Re: one hour checkpoints
- From: "Christo Kutrovsky" <kutrovsky.oracle@xxxxxxxxx>
- To: ax.mount@xxxxxxxxx
- Date: Wed, 24 Jan 2007 11:17:12 -0500
Well, in theory, 600mb of redo log could be 1'228'800 blocks changed.
That's 629145600 bytes of redo log, with a redo record been 512 bytes.
That's only an approximation, since you could have merged records,
multiple changes in a single record and etc.
Let's assume a typical IO time of 5 ms. That would be 1228800*5ms =
6'144'000 ms = 6'144 seconds = 1.7 hours.
So it could've taken 1.7 hours. And that's been optimistic about the
5ms IO. It could've been 10 ms during busy times.
It's not as bad as it sounds.
--
Christo Kutrovsky
Senior Database/System Administrator
The Pythian Group - www.pythian.com
I blog at http://www.pythian.com/blogs/
On 1/18/07, amonte <ax.mount@xxxxxxxxx> wrote:
Hello all
I have a quite busy Oracle APPS database running in HPUX. Today during peak
hour I saw this in alert
Thu Jan 18 10:19:50 2007
Beginning log switch checkpoint up to RBA [0x17d1.2.10], SCN:
0x0784.b14a52c1
Thu Jan 18 10:22:09 2007
Beginning log switch checkpoint up to RBA [0x17d2.2.10], SCN:
0x0784.b14a8673
Thu Jan 18 10:26:18 2007
Beginning log switch checkpoint up to RBA [0x17d3.2.10], SCN:
0x0784.b14aee22
Thu Jan 18 10:51:32 2007
Beginning log switch checkpoint up to RBA [0x17d4.2.10], SCN:
0x0784.b14d0ddb
Thu Jan 18 11:09:24 2007
Beginning log switch checkpoint up to RBA [0x17d5.2.10], SCN:
0x0784.b14ea5dd
.........................
Thu Jan 18 11:12:04 2007
Completed checkpoint up to RBA [0x17d1.2.10], SCN: 0x0784.b14a52c1
Thu Jan 18 11:16:19 2007
Completed checkpoint up to RBA [0x17d2.2.10], SCN: 0x0784.b14a8673
Thu Jan 18 11:16:45 2007
Completed checkpoint up to RBA [0x17d3.2.10], SCN: 0x0784.b14aee22
Thu Jan 18 11:18:22 2007
Completed checkpoint up to RBA [0x17d4.2.10], SCN: 0x0784.b14d0ddb
Thu Jan 18 11:23:56 2007
Completed checkpoint up to RBA [ 0x17d5.2.10], SCN: 0x0784.b14ea5dd
From v$log_histroty I see the log switch frequency
select * from v$log_history
where FIRST_TIME > ('20070118 090000');
RECID STAMP THREAD# SEQUENCE# FIRST_CHANGE#
FIRST_TIME NEXT_CHANGE#
---------- ---------- ---------- ---------- ----------------------
--------------- ----------------
6096 612181190 1 6096 8266491016370 20070118
090018 8266491515585
6097 612181328 1 6097 8266491515585 20070118
101949 8266491528819
6098 612181578 1 6098 8266491528819 20070118
102208 8266491555362
6099 612183092 1 6099 8266491555362 20070118
102618 8266491694555
6100 612184164 1 6100 8266491694555 20070118
105132 8266491799005
6101 612185404 1 6101 8266491799005 20070118
110923 8266491936643
Redo log are 600MB each.
How can a checkpoint take so long?
Cheers
Alex
--
Christo Kutrovsky
Senior Database/System Administrator
The Pythian Group - www.pythian.com
I blog at http://www.pythian.com/blogs/
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