RE: a doubt of savepoint

王旭 Mon, 18 Apr 2005 18:55:52 -0700

thanks,Hahn.

But i also have some questions.

One,IS the logvolume in the hard disk or in the memory?

Two, Do the savepoint activate the write process only?

In oracle,there are two important process:DBWR and LGWR.DBWR control datas write operation from memory to disk and LGWR control logs write operation from memory to disk.There are many event can trigger DBWR and LGWR.e.g,when commit,when 1/3 of redo log buffer(in memory) be used,when checkpoint activation .....

I understand only savepoint can activate the write process in maxdb from your answer.I don't know if it is right for my understanding.

Where can i find the documents about the read and write mechanism of maxdb? thanks.

From: "Hahn, Uwe" <[EMAIL PROTECTED]>
To: "? ?" <[EMAIL PROTECTED]>, <[email protected]>
Subject: RE: a doubt of savepoint
Date: Mon, 18 Apr 2005 14:23:37 +0200

Hello Liu,

MaxDB's savepoint is similar to Oracle's checkpoint.

If no other reason caused a savepoint a savepoint is written if since the

last savepoint 2/3 of the logvolume is used.

If no other reason caused a savepoint and 5000 Log writes were done in at

least 600 sec (default) a sapoint is triggered.


Kind regards,
Uwe

>-----Original Message-----
>From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
>Sent: Monday, April 18, 2005 1:30 PM
>To: [email protected]
>Subject: a doubt of savepoint
>
>    In maxdb help,there is a part of savepoint document:
>
>    As savepoints affect system performance, the database
>system does not
>perform a new savepoint automatically at the end of this time
>interval. It
>waits for 5,000 I/O operations and only then does it check how
>much time
>has elapsed since the last savepoint. This means that the
>system does not
>write a savepoint unless at least 5,000 I/O operations have
>taken place
>since the last savepoint. With a lower number of I/O
>operations, more time
>may elapse until the next savepoint.
>
>    And the "_Restart_time" is 600 sec!
>
>    Too long to active database writer and log writer.
>
>    In oracle,there is a concept named "checkpoint".I don't
>know whether
>"chechpoint = savepoint"
>
>   thank!
>
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RE: a doubt of savepoint

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