Oracle Data Blocks

[amolso]

How the Data Blocks in Oracle tablespaces are allocated by oracle ?
It is said that
"The Data Block size should be integer multiple of operating system block size to save I/O wastage"

if I understand it correctly , are no. of bolcks created automatically based on size of tablespace and size of table
(initial, next storage) ?

Does this means that in create table definition "next" storage parameter should be the multiple of OS block size
Or "initial"should also be a multiple of block size?

Is it like that "initial" and "next" parameters should be like 512K or 256K or 128K?

What can be the idea of avoiding I/O wastage ?
Amol

[sig][/sig]

 

[karluk]

I'm sure the "Data Block size" means the parameter "db_block_size", which is fixed at database creation time. It represents the amount of data read from (or written to) disk during every Oracle i/o. It is typically 2k, 4k, or 8k, and should, as your documentation indicates, be a multiple of the os block size.

The values of initial and next extent are not quite the same thing. An extent will typically consist of many data blocks. It seems to me that a good extent size would be a multiple of the db_block_size, and so would also be a multiple of the os block size.

I replied to one of your earlier posts with the recommendation to use extent sizes of 160k, 5120k, and 160m. This is by no means the only reasonable space allocation strategy, but notice that if you choose to follow it you will get extent sizes that are multiples of db_block_size. [sig][/sig]

 

[carp]

You should also try to make extents a multiple of DB_FILE_MULTIBLOCK_READ_COUNT if you anticipate frequent full table scans on the segment. [sig][/sig]