Defragmentation on system level

Question

Do as in the DB I have no defragmentation,
So at the operating system will not have defragmentation?.
Are the blocks in the extent always arranged in the same place the disk and in sequential order?
Is when Oracle allocate new extents they always arranged in sequence on the disk (assuming the table is one file)?
In eneral my question is
when Oracle creates a file (DATA FILE) file is created in the same place on the disk?

Answer 1

Sagi wrote:
Do as in the DB I have no defragmentation,
So at the operating system will not have defragmentation?.
Are the blocks in the extent always arranged in the same place the disk and in sequential order?
Is when Oracle allocate new extents they always arranged in sequence on the disk (assuming the table is one file)?
In eneral my question is
when Oracle creates a file (DATA FILE) file is created in the same place on the disk?You need to understand that Oracle is several layers of abstraction away from that spinning platter. In all but the most primitive of systems, even the OS is a few layers of abstraction away. At oracle's level .. even at the os level .. the concept of "contiguous" is really only "logically contiguous addresses" that have nothing at all* to do with the physical reality of read/write head position and cylinder/track/sector location on the disk.
And don't forget that by the time the I/O request gets to the real physical level, it is done in terms of the sector on the platter, not the OS or database block. The sector size is determined by the hardware microcode, not the OS.
Spend a few minutes thinking about the implications of that.
Then throw in the complexity of a multi-user system, and the fact that once the disk and read/write head have completed an I/O operation on your behalf at their level, they will go service a request for some other user or process totally unrelated to your process.
Edited by: EdStevens on Oct 16, 2010 10:28 AM