Re: "control file sequential read" on RAC

Afternoon all,

>> "Alex Gorbachev" <gorbyx_at_gmail.com> 05/15/07 01:28PM >>>
>> Seems like it's inefficient execution plan.
>> I know that Oracle might go crazy joining dictionary views and V$
>> views.

I've been told by Oracle trainers that joining a V$ view to an physical table or other dictionary tyope objkect is fraught with danger because :

• the V$ stuff is memory based and not protected by read consistency
• the V$ stuff changes frequently

When you join V$ to others, each time the V$ changes, Oracle starts the query again. It only finishes when it manages to join all of V$ with whatever without a change occurring part way through.

I used to join V$SESSION_WAIT to DBA_OBJECTS and performance was abysmal :o(

Cheers,
Norman.

Norman Dunbar.
Contract Oracle DBA.
Rivers House, Leeds.

Internal : 7 28 2051
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