1.) Correct, except that the DBA can always shrink it manually. 2.) Well, that's true, but a rollback segment w/ optimal set could conceivably grow to fill the tablespace as well. It depends on the size of the rollback tablespace and the size(s) of your transaction(s). The reason that it's perceived that not having optimal set exacerbates it is probably due to the fact that without optimal, the rollback segments never shrink. So, one occurrance of a very large or runaway transaction can bloat a particular rollback segment. That permanently decreases the free space in the tablespace. Over time, multiple rollback segments could become bloated, and eventually, you run out of space. In the case where optimal is set, this is less likely to happen, because the rollback segments will shrink, and the cumulative effect never occurs.
3.) Not at all. ORA-1555s can occur whenever the size or number of rollback segments is inadequate. Systems can be constructed where ORA-1555 is inevitable. (For example processes doing lots of DML concurrent with processes that execute long running queries.) There's been a *LOT* written on ORA-1555 over the years. If you have specific problems or questions, start w/ MetaLink if you have access. If not, check out these URLs: http://www.jlcomp.demon.co.uk/faq/snapshot.html http://www.jlcomp.demon.co.uk/faq/settrans.html Hope that helps, -Mark -----Original Message----- From: A Joshi [mailto:[EMAIL PROTECTED] Sent: Sun 12/28/2003 1:39 AM To: Multiple recipients of list ORACLE-L Cc: Subject: Re: ** can two processes use the same rollback extent Hi, A simple rollback segment question. If I do not set a optimal then can I assume following 1) rollback segment will not shrink. 2) It will keep growing till tablespace fills up. 3) And there will be no 'snapshot too old' errors? Thanks A Joshi <[EMAIL PROTECTED]> wrote: Hi, One rollback segment can be used by multiple transactions/processes but what about the extents? Is it safe to assume that only one transaction/process can use one extent? What is a good way to size the extent for warehousing tasks? Or guess the rollback generated and size needed. Thank You --------------------------------- Do you Yahoo!? Protect your identity with Yahoo! Mail AddressGuard --------------------------------- Do you Yahoo!? Protect your identity with Yahoo! Mail AddressGuard
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