On Fri, Feb 22, 2008 at 7:52 AM, Sam Bootsma <sbootsma@xxxxxxxxxxxxxx> wrote: > 1. Have you found Incremental backups and Change Block Tracking to be > reliable; i.e, can you reliably backup and then restore and recover? > > Incremental level 1 backups with BCT are much faster than level 1's without BCT. Restore is not a problem. Level 1 backups are a very good thing. Let's say you took a level 0 yesterday. Last night a batch job loaded a table in direct path mode, which will not appear in the archive logs. Today you do a level 1 incremental. The blocks loaded in direct path mode will be backed up by the level 1, as they are recorded in the BCT. So in the event of recovery, the level 1 backup not only skips all the archive logs from the end of the level 0 to the beginning of the level 1, the table loaded with direct path will also be recovered, which would not have happened with the level 0 + archive logs. > > > 2. What about Oracle compression during an RMAN backup? Is that reliable? > > Haven't heard any problems of reliability. You may want to test it however, as my tests have shown quite a CPU hit. > 3. How much of a performance hit using the Change Block Tracking feature? > What about Oracle compression? > > > < 1% according to Oracle. I haven't measured the actual CPU usage of compression, only its effect on a running database. > 4. Do you know if any of these features are additional cost? Do you know > if there is a view in Oracle that outlines what features come with EE and > what features are additional cost? > > Can't answer that. > > > 5. We also have the option to do compression at the tape drive level. Is > anybody aware of any reason that Oracle compression (during backup) would be > better or worse than letting the tape drive do it? > > > Tape level compression is probably faster. A problem there might differing implementations of the compression between different versions of tape firmware. Might be a problem if you need to restore old tapes with new hardware. 6. I have read that restores of a cumulative backup a generally faster than > restores of a differential backup. What makes cumulative faster? Is it > simply that RMAN will just one incremental file to restore and recover from > (plus archive logs)? If there are six differential backups to recover from, > RMAN should be able to restore and recover the six files without DBA > intervention. I don't see a significant time difference. Perhaps a couple > minutes extra because it has six more files to deal with? > > Haven't tested it, don't know. -- Jared Still Certifiable Oracle DBA and Part Time Perl Evangelist