Re: Excessive Logical and Physical I/O

Well spotted.....

The I/O waits were all (or most) due to sequential I/O to datafile 14 (the rollback segment tablespace).

So the excessive reads were due to the query having to build a read consistent view of the table blocks.

My next question is: Would large rollback segments (i.e. overextended) make this read consistent build process much slower..?

The rollback segments have overextended to nearly 2Gb (2000 extents).

Would this have a (noticeable) negative impact on the speed of the read consistent build process...?

The reason I ask this is because I have tested this out in our TEST environment and all other things being equal, the query runs very quickly in TEST.

The only difference is that the rollback segments are much smaller in TEST (15 Mb). The size difference is due to an OPTIMAL setting in TEST. Thanks for you time...

Matt Received on Thu Mar 18 2004 - 02:26:49 CST