Hi Ian, Little correction. *Sometimes* index full scan (IFS) also uses multiblock IOs. In this case number of blocks is controlled with _db_file_noncontig_mblock_read_count. If my memory servers me right the default value is 11 for 8.1.7 on Solaris. You can easily check out this by using 10046 event, level 8. My assumption is that IFS may use multiblock IOs for reading leaf blocks and it always use single block IOs for reading branch blocks. I said may because I believe it somehow depends on index structure and on the other hand IFS *must* preserve index order.
Regards, Ed > You are right Fast Full Scans use multiblock IO. Other index scans do not. That >had slipped by me. So my speculation is moot. If it was an FFS, I could come up with a scenario where such a path would be better than range scan. But that's moot, and I'm pretty sure such scenarios are beyond Oracle's optimizer. > > Ian MacGregor > Stanford Linear Accelerator Center > [EMAIL PROTECTED] > -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Edward Shevtsov INET: [EMAIL PROTECTED] Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (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).
