Consideration in chosing DMS container type

[Prasad]

Hi,

What are the different considerations/guidelines in chosing raw device
or file containers for DMS tablespaces?

A link would be very helpful.

Thanks,
Prasad.

[Mark A]

On May 2, 11:54 am, Prasad <[e-mail]:

Hi,

What are the different considerations/guidelines in chosing raw device
or file containers for DMS tablespaces?

A link would be very helpful.

Thanks,
Prasad.

There is not much difference in performance. I would only consider raw
for a data warehouse with a lot of table scans, and even then I might
used cooked files.

If you have an OLTP system with almost all access via indexes (except
for small tables), then I would not even consider raw.

[Ralph Ganszky]

>

What are the different considerations/guidelines in chosing raw device
or file containers for DMS tablespaces?

Hi,

I have no link for DB2. But you may use
http://www.jlcomp.demon.co.uk/raworfs_i.html which discusses a bit the
differences between raw and cooked files. The information's there are not up
to date, but it is may be interesting to read how you could figure it out
what you should do to get optimal performance in your environment. Its
written for Oracle, but not everything is different between Oracle and DB2.

I don't know all operating systems, but I could tell you, that on Solaris (9
& 10) you should switch on forcedirectio for the database containers and the
logs. This will allow parallel writes to cooked files like you would achieve
it with raw devices. On HP-UX (11.23) you don't have this option. There
writers block writers on cooked files. The negative performance impact could
be lowered by creating more and smaller containers. On huge databases with
lots of connections you may be have to create less containers on HP-UX to
reduce the amount of open files.

But the bottom line is, you have to find it out for your application and
your workload. We run all databases with cooked files, but our databases
haven't reached 10TB yet. May be we have to decide differently in the
future.

Best regards
Ralph

[=?iso-8859-1?Q?Joachim_M=FCller?=]

Prasad,

There are two really good papers for that what you ask, one for DB2 UDB and
one for Oracle:
http://www3.software.ibm.com/ibmdl/p...IO-article.pdf

http://www-03.ibm.com/servers/aix/wh...b_perf_aix.pdf

Best regards,
Joachim Müller

"Prasad" <ba*******@gmail.comschrieb im Newsbeitrag
news:11*********************@c35g2000hsg.googlegro ups.com...

Hi,

What are the different considerations/guidelines in chosing raw device
or file containers for DMS tablespaces?

A link would be very helpful.

Thanks,
Prasad.

[Prasad]

Our architects decided to use RAW devices. Thank you all for your
responses.