Re: Performance issue during datafile resize

On Fri, 30 Dec 2005 16:58:14 -0800, VIC wrote:

> It seems the datafile resize action actually slow down/block
> transactions, if those transactions are hitting the file being resized.
> Could someone tell me the details mechanism behind datafile resize
> process?

Well, Oracle computes how many bytes it needs to add, writes those bytes at the end of the file in block by block fashion, using "writev" system call, locks the datafile header for writing, updates the bitmap and releases the lock. If transactions are actually allocating new extents while the bitmap is being updated, which is entirely possible in autoallocate tablespaces as they allocate very small extents, they will have to wait. If the file has been made significantly larger, new extent may need to be allocated to extend the bitmap and whole thing will be even slower.

-- 
http://www.mgogala.com