Re: Multiblock_read_count setting

This is what Oracle Server Reference states:

DB_FILE_MULTIBLOCK_READ_COUNT operating system–dependent

Used for multi–block I/O, this is the maximum number of blocks read in one I/O operation during a sequential scan. The default is a function of DB_BLOCK_BUFFERS and PROCESSES. Values in the range of 4 to 16 or even 32 are reasonable.

The actual maximums vary by operating system; they are always less than the operating system’s maximum I/O size expressed as Oracle blocks (max_IO_size/DB_BLOCK_SIZE), and can never be larger than DB_BLOCK_BUFFERS/4. For information on the optimizer, see Oracle7 Server Tuning.

See also your operating system–specific Oracle documentation for the default value.

Hope this helps

Sunit

Dave Morgan wrote:

> Hello all,
> I understand that the multi_block read_count parameter is
> used when doing full table scans. However, I do not understand
> which blocks are being refered to (db, os or physical disk) or
> what the setting should be.
>
> Our current databases are:
>
> Oracle 7.2.2.4 on Solaris 2.5.1
> No RAID, no mirroring just standard SCSI
> Database block size = 8kb
> database_block_buffers = 14000
>
>
> The settings I inherited for the multiblock_read _count
> range from 4 to 256.
>
> Any suggestions, answers or ideas welcomed.
>
> Dave
>
> / Dave Morgan, Database Administrator
> / QC Data Petroleum Services Ltd.
> / E-Mail: dave_morgan_at_calgary.qcdata.com
> / http://www.qcdata.com
> /
> /I am allowed to have opinions. If my wife approves of them I am allowed
> /to have them.
Received on Thu May 21 1998 - 15:20:46 CDT