RE: raw devices

But probably there is some other resource that replaces the ST enqueue to control concurrency in case of LMT tablespaces and the update of the bitmap headers.

Waleed

-----Original Message-----
Sent: Tuesday, August 13, 2002 2:35 PM
To: Multiple recipients of list ORACLE-L

On OPS and RAC, the issue is not really the contention for the UET$ and FET$ tables themselves. It is the contention for the "ST" enqueue/lock which is global across all instances. Only one session on one instance can hold "ST" across all instances in the OPS/RAC database. Essentially, all dictionary space-management operations become single-threaded across all instances, which is avoided by using LMT...

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Tuesday, August 13, 2002 9:23 AM

> Hello,
>
> Some may not agree with this sentiment, but unless there is an overriding
> reason for your needing to switch from dictionary-based tablespaces to
> locally-managed, I would leave well enough alone. Our OPS started out
doing
> many things wrong, which we straightened out as we got more sophisticated
> about middle tiers, various contention issues, set up better granularity
for
> locks, etc. One thing that we decided to leave in place was the
> dictionary-based tablespaces. We decided that it was more effort to modify
> the production system than would be gained by a small reduction in
> contention for $UET and $FET. If we were creating a new OPS, we would use
> locally-managed. With respect to the raw device allocation, our UNIX guy
set
> up the devices in /dev/vg0x, and the DBAs create links (ln -s) in
> /u01/oradata/DB_name to those devices. When we drop a tablespace, we break
> the links. For a new tablespace, we create new links. This way we have
> client-specific datafile names in /u01/oradata/DB_name. And we created the
> devices based on some growth assumptions, so DBAs do not have to chase
after
> UNIXAdmin every month to add more raw devices.
>
> Thank you,
>
> Paul Sherman
> DBA Elcom, Inc.
> email - psherman_at_elcom.com
>
>
> -----Original Message-----
> Sent: Tuesday, August 13, 2002 10:19 AM
> To: Multiple recipients of list ORACLE-L
>
>
> You do not have to do anything on Unix. Once you drop the Tablespace the
> raw file (device) could be used immediately in a new TS.
>
> Regards,
>
> Waleed
>
> -----Original Message-----
> To: Multiple recipients of list ORACLE-L
> Sent: 8/13/02 9:38 AM
>
> Hi,
>
> Wondering if anyone can help me with this question. Basically we have a
> parallel server setup (solaris 2.8 oracle 8.1.7.3)and so are using raw
> devices. I am in the process of recreating the tablspaces to be locally
> managed as opposed to dictionary. My question is this: In a filesystem
> environment, I would drop the tablespace in oracle and rm the
> corresponding datafile on the unix level, and then I can go about
> recreating my tablespace. I know that the OS doesnt really "interact"
> with the raw devices as such, but, in this situation would I be able to
> drop the tablespace and recreate it without having to do anything on the
> unix level? Would that corresponding raw device just be overwritten??
>
> Any help would be greatly appreciated
>
> Rgds
>
> Fawzia
>
>
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> Author: Khedr, Waleed
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