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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Script to overcome ORA-54 during DDL
I've used something like this in the past, except I also exclusively lock
the table to which I am trying to apply the DDL.
The idea being that I wait to get the exclusive lock, and having got the
exclusive lock the DDL can acquire the lock in nowait mode. Its not
perfect, but I find I need less attempts to get the DDL to execute.
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Jonathan Lewis
Sent: 25 June 2004 21:37
To: oracle-l_at_freelists.org
Subject: Re: Script to overcome ORA-54 during DDL
This looks about right (except for the formatting);
create or replace procedure do_ddl(m_sql varchar2)
as
in_use exception ;
pragma exception_init(in_use, -54);
begin
while true loop
begin
execute immediate m_sql;
exit;
exception
when in_use then null;
when others then raise;
end;
dbms_lock.sleep(0.01);
end loop;
end;
/
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk/faq/ind_faq.html The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/seminar.html Optimising Oracle Seminar - schedule updated May 1st
Sometimes when trying to perform DDL on really hot objects (heavy read/DML), I get:
ORA-00054: resource busy and acquire with NOWAIT specified.
I guess this is because you need to obtain a library cache lock in order to change the object definition. Since there is no enqueue mechanism for this resource, you can't just 'lock table ... in exclusive mode;' All that gives you is a DML lock.
One way to avoid this is to write a PL/SQL routine that uses DBMS_SQL and spins trying to run the DDL, stopping only when it succeeds. This seems to work most of the time.
Does anyone have a script for doing the above that they would like to share?
Please don't tell me to just use dbms_redefinition. That is unnecessarily complex when the above technique can be used instead.
Thanks
--
Jeremiah Wilton
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