Re: Informix versus oracle
Daniel Morgan <damorgan@exxesolutions.com> wrote in message news:<3ED56F59.E4AB489D@exxesolutions.com>... > "Milton J. Vidrine, Jr." wrote: > > > Here are a few of the differences (or similarities, depending on how you > > look at it): > > > > Informix Oracle > > Raw disk space File system > > Logical logs Redo logs > > Physical log Rollback segment > > dbspace,dbslice tablespace > > shared memory sga > > (no correlation, OS auth) password file > > > > From what I have seen in Oracle DBA class and Backup / Recovery class, there > > is about an 85% correlation between Informix and Oracle as far as basic > > operation is concerned, other than terminology. > > > > HTH > > Milton J. Vidrine, Jr. > > > > Your knowledge of Oracle was current with what version? ;-) > > Both can use raw disk space. > > Oracle 9i no longer uses rollback segments by default and Oracle has announced > their elimination in future versions, 10i being due out in a matter of months. > > But, while I'd never feel comfortable putting a percentage on it you are roughly > correct, > the products are similar but with different architectures. In 9i you have the option of using Rollback segments instead of the default of UNDO segments. Similar functionality (used for transaction consistency) but one or the other has to be there. Another powerpoint change to the "architecture"
David Summers wrote: > Daniel Morgan <damorgan@exxesolutions.com> wrote in message news:<3ED56F59.E4AB489D@exxesolutions.com>... > > "Milton J. Vidrine, Jr." wrote: > > > > > Here are a few of the differences (or similarities, depending on how you > > > look at it): > > > > > > Informix Oracle > > > Raw disk space File system > > > Logical logs Redo logs > > > Physical log Rollback segment > > > dbspace,dbslice tablespace > > > shared memory sga > > > (no correlation, OS auth) password file > > > > > > From what I have seen in Oracle DBA class and Backup / Recovery class, there > > > is about an 85% correlation between Informix and Oracle as far as basic > > > operation is concerned, other than terminology. > > > > > > HTH > > > Milton J. Vidrine, Jr. > > > > > > > Your knowledge of Oracle was current with what version? ;-) > > > > Both can use raw disk space. > > > > Oracle 9i no longer uses rollback segments by default and Oracle has announced > > their elimination in future versions, 10i being due out in a matter of months. > > > > But, while I'd never feel comfortable putting a percentage on it you are roughly > > correct, > > the products are similar but with different architectures. > > In 9i you have the option of using Rollback segments instead of the > default of UNDO segments. > Similar functionality (used for transaction consistency) but one or > the other has to be there. > Another powerpoint change to the "architecture" Hardly a PowerPoint change. The architecture is very different with undo. 1. SET TRANSACTION USE ROLLBACK SEGMENT ... gone. 2. You can now set undo retention in minutes so that if sufficient disk space is available it is possible to recover 24 hours of transactions without ever touching off-line backups. I know people running with undo sized to handle even more. 3. DBMS_FLASHBACK package allows for flashback queries so that it is easy to see the state of any table or tables at any point in time within the undo retention window and, if necessary, easily recover a table to a point in time or to the point before a specific transaction (try to do that with backup tapes and rollback segments). 4. The near elimination of the dread ORA-01555 error message due to rollback segments being flushed The reason for the name change is far more than cosmetic (as unfortunately is true of so many of Oracle's name changes). In this case the differences are both substantial and substantive. -- Daniel Morgan http://www.outreach.washington.edu/extinfo/certprog/oad/oad_crs.asp damorgan@x.washington.edu (replace 'x' with a 'u' to reply)