Re: Huge memory consumption during hot backup

Paolo wrote:

> Hi,
> I'm using Oracle 8.1.7.4.1 on Windows 2000 Advanced Server SP 3.
> The DB is in archive log mode, and I use the following script to
> perform an hot backup:
>
> -------------------------------------------------------
> spool temp_bk_res
> $SET backup=x:\backup
> connect user/password_at_mydb as sysdba
> $mkdir x:\backup\today
> alter tablespace GENESYS_CFG begin backup;
> $copy Y:\ORACLE\ORADATA\MYDB\USERS01.DBF x:\backup\today
> alter tablespace GENESYS_CFG end backup;
> alter tablespace GENESYS_LOG begin backup;
> $copy Y:\ORACLE\ORADATA\MYDB\USERS02.ORA x:\backup\today
> $copy Y:\ORACLE\ORADATA\MYDB\USERS02.ORA x:\backup\today
> $copy Y:\ORACLE\ORADATA\MYDB\USERS02.ORA x:\backup\today
> alter tablespace GENESYS_LOG end backup;
> [...]
> -------------------------------------------------------
>
> My problem is that when I begin the backup the available physical
> memory decreases by around 400-500Mb, and if my system have less free
> memory than requested it begins to swap a lot, making the database
> unable to reply to the application (which hang).
>
> I've tried also by replacing the "$copy" commands with the "$start
> /wait /low ocopy" commands, but the memory consumption has not
> changed; besides, I tried to change Windows' file cache usage, by
> setting the "File and Printer Sharing for Microsoft Networks"
> properties to "Maximize data throughput for network applications", but
> with no success.
>
> Do you have something to suggest?
>
>
> Best regards,
>
> Paolo Borghesi

What I'd *really* suggest is to use RMAN to do your backups.

But if RMAN is absolutely not on, then I'd suggest having a look at the sort of Windows Scripting Host script I have available at

http://www.dizwell.com/html/scripted_backups.html

I've run that against many databases, and it doesn't have anything like the memory hit you are talking about.

(As the site says, I hope: although the script has one 9i specific bit in it, it runs on 8i just fine so long as you edit the 21 lines bit to whatever is appropriate to 8i).

I'd be interested, in any case, to see whether you can replicate your memory drop using it. If you can, something serious is up. If you can't then it's something in the script you are already using.

Regards
HJR Received on Thu Sep 16 2004 - 19:03:35 CDT