Too many sessions inserting in table

Question

Hi All
I am new to batch programs processing .Please help me on this.
I have an application in which more than 1 session
will try to insert millions of recrds in the same table.
I need to know what care should I take for this.
Will tables be locked or I do not need to wory about this
Further in the program , one application may delete certain lacs of records while
other session might still be inserting into it
WHat do I do in this case.
Also if one session is trying to update while other session is inserting/deleting records
then what care do I take
Thanks
Ashwin N.

Answer 1

It is a very bad idea to have more than one session attempt to insert millions of rows (if that is a literal statement of requirement). In you have paid for it use the Parallel Server option, but always try to have only a single batch process running unless it is absoultely unavoidable. Otherwise you are increasing the risk of latch contention both for the table itself and also rollback segemnts.
Other things to check (these are database type things):
- have big rollback segment assigned to batch session;
- consider committing every 1000 records to cut down on rollback usage;
- if you're really going to have several sessions doing monster inserts like this give your table lots of freelist groups;
- make sure the table and its indexes have enough empty space by pre-assigning extents
- make sure that the tablespaces are big enough in case additional extents are required
As for row contention: rows you insert cannot locked by someone else nor are they affected by someone else inserting, updating or deleting other rows (although you might suffer from block header contention) unless that other session has issued a LOCK TABLE statement. Only once you have committed your insert will other sessions be able to see, update and delete your new rows (because Oracle doesn't support DIRTY_READ :-) )
One way of reading your question is that you think someone may be trying to delete the records you're inserting. I hope that's not the case but if it is someone ought to have a look at the business model.
rgds, APC