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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Snapshot Too Old Error on Export !!!
It would have to be using rollback segments. That's where it would read the consistent view of data blocks from that had been changed since the start of the export.
>>> Sunil_Nookala_at_Dell.com 02/21/03 01:14PM >>>
Stephen,
My understanding is having consistent=y uses no rollback, since the changes
occurring
during the export are not being captured in the export dump.
on few occasions i've still got the spurious ora-1555(snap shot too
old)error on exporting a 80GB highly
transactional database which terminates the export.
am i thinking wrong?? help!!
Sunil Nookala
DBA
3-4502
907-9255(pager)
-----Original Message-----
Sent: Friday, February 21, 2003 10:35 AM
To: Multiple recipients of list ORACLE-L
I would echo a previous post that you can't backup a database with the export utility. I suspect you get your error because you are using consistent=y in the export. The database is trying to give you data as of the time you started the export. The fact that you are getting the snapshot too old message is evidence that the data is changing while you are exporting -- to the extent that the database is eventually unable to keep doing it -- but these data changes will not be in the export file.
A genuine backup using rman or the old alter tablespace begin backup method is the only "proper backup".
If you are trying to get production data to move into a test/development database schema, then export is certainly the most convenient way of doing it. If you are, in fact, trying to backup the database, here is something to get you started.
If the filesystem to which your export file is going is big enough, consider using that filesystem to store a database backup instead of an export. Assuming it is /where/it/goes, try the following:
Make sure sys (or system, if you prefer) has been granted sysdba in the
database.
Create two files with text similar to the following:
for file named backup_database.rcv:
-------------- snip -----------------
tag backup_db_full
(database include current controlfile);
release channel ch1;
}
------------- snip --------------
This will backup the database.
for file named backup_arch.rcv
------------- snip ------------
run {
allocate channel ch1 type disk format '/where/it/goes/%U_ARCH';
set command id to 'rman';
change archivelog all crosscheck;
backup
(archivelog all delete input);
backup ***This line and the next if you are duplexing archived logs***
(archivelog like '/directory/where/duplexed/archivelogs/are/%' delete
input);
release channel ch1;
allocate channel ch1 type disk format '/where/it/goes/%U_CONTROL';
backup current controlfile tag='backup';
release channel ch1;
sql "ALTER DATABASE BACKUP CONTROLFILE TO
''/where/it/goes/CONTROL_FILE.BAK'' REUSE";
}
------------ snip ----------------
To run a backup, type in the following commands:
rman nocatalog
connect target sys/qwerty_at_DBNAME
@backup_database.rcv
@backup_arch.rcv
exit
Now, make sure you backup /where/it/goes directory to tape with whatever operating system backup utility you are using.
One thing that can be added, if you want to be extra thorough, is to put in a log switch followed by an archive log current, after you run the archivelog backup. Then you run ANOTHER archivelog backup. In the world of Murphy's Law, you do it this way because your archive_log_dest will, some day, at the worst possible time, be unable to accommodate a log switch and archive log current. So you clean it out first prior to the log switch.
It might be useful to know how to restore the database ... that's just something I saw written on a toilet stall wall. It seems reasonable. ("... He who reads these words of wit, eats those little balls of ... ") I think the subject is probably more extensive than can be covered in a simple e-mail; so I won't try to cover it all. But, in it's simplest form, a recovery looks like:
If the last rman backup has been deleted from /where/it/goes, restore those files from tape.
startup mount the database (assuming the control file is NOT the thing you are restoring)
rman nocatalog
connect target sys/qwerty_at_DBNAME
allocate channel ch1 type disk;
restore database;
restore archivelog all;
recover database;
release channel ch1;
open the database.
See, rman isn't so bad. It's biggest problem is that, if you start to like it, then it can lead to other things such as liking vi, growing a beard, and wearing suspenders.
(Obviously, I have a rare day here where I don't have a lot to do. Hence, the verbose reply.)
> -----Original Message----- > Could somebody help me here, this is very critical to be running > production without proper backups .....! >
-- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Stephen Lee INET: Stephen.Lee_at_DTAG.Com Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: INET: Sunil_Nookala_at_Dell.com Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Darrell Landrum INET: DLANDRUM_at_zalecorp.com Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Fri Feb 21 2003 - 15:48:54 CST
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