Re: Export and 1555 errors

Matt Riggsby <Matthew.Riggsby_at_novainfo.com> schreef in berichtnieuws 397b5de2.0304170950.2288b129_at_posting.google.com...
| We're trying to export the contents of a large 8.1.7 database with the
| EXP command, but we're consistently getting error 1555 (snapshot too
| old: rollback segment...too small). I gather this means that the
| export process is trying to load entire tables into a rollback segment
| and running out of room. The prescribed fix for this is to make sure
| that the CONSISTENT parameter isn't Y. However, we've got
| CONSISTENT=N in the EXP command (and I *think* that the rollback
| segments should be able to grow large enough to contain most of the
| tables anyway, although I'm not positive). What else should I be
| looking at?

First: export does not load the entire table in the rollback segments. Maybe you should read about what rollback segments are for. Second: export does only selects, so it will not use the rollback segments, so there is no need to let them grow (except for the "delayed block cleanout" which I'am not going to explain, I hope the real experts on this will post that).

When you make a consistent=n export each table is exported consistent (where consistent=y makes the total export consistent), that is: the table is exported as it was at the moment the export of that table started. When the table is updated during export, export needs the rollback segments to reconstruct the data as it was at the beginning. It reads the rollback segments for that. ORA-1555 occurs when that info (previous versions of blocks) is no longer available in the rollback segments. There must be other activity in your datatabase that updates the table, commits it and thereby freeing the rollback space for re-use. Try export again after making the (optimal) size of the rollback segments bigger, so there is less chance the rollback data is overwritten before you need it. Received on Thu Apr 17 2003 - 13:35:29 CDT