Replacing / Compiling Database Triggers in a HA/High Load system

Question

Hi there,
My collegue has just asked me if downtime needs to be scheduled to replace an After IUD Database trigger where I've made a minor change.
If this were a package or procedure, the answer would be an obvious yes, as I'd be wary of my users getting the dreaded: ORA-04068... State of Package has been disguarded.
What about when working with database triggers?
If the trigger is firing at the same time that I perform my Create or Replace Trigger DDL, will everything fall into a screaming heap?
Notes:
Oracle 10g R2 db.
High DML rates on the table that the After IUD Trigger is 'attached' to.
It's a near certainty that when the Create or Replace Trigger DDL runs, the trigger will be active at the time.
The Trigger is 'simple' in that it's use: is to call a DB package with some of the :new values as params.
+(I'm happy to rtfm - if someone can tell me where!!)+
Cheers -
Ron Marks

Answer 1

If this were a package or procedure, the answer would be an obvious yes, as I'd be wary of my users getting the dreaded: ORA-04068... State of Package has been disguarded.Not true. This exception is thrown only if sessions have some state represented in package variables. If there is no associated session state, then no exception would be thrown after recompile.
If the trigger is firing at the same time that I perform my Create or Replace Trigger DDL, will everything fall into a screaming heap?You'll wait - to lock an object in library cache which represents your trigger. Not sure if this would require a library cache lock on underlying table, but I would guess that it is required. BTW, locking a table would make no any sense: CREATE TRIGGER is a DDL, which means before it began it issues a COMMIT => all locks are released, and it is quite possible that a TM lock for CREATE TRIGGER won't be acquired since resource would be busy.
Oracle 11gR2 claims to address problems of application upgrades on a high-load environments with a feature called "Editions" (not a good name - try to find something about it via Google...)