Will there be any performance impact

Question

Hi All,
    Currently i'm having table employee with 1 millon records.. (emp ID is primary key). In process , i want to insert new employee ID and use for program and deleting it finally(simplyfing changes in current program).. every day this will take 100K trancations.
   I'm planning to commit only after delete. (ie insert -> make some update --> delete the same row --> commit).
Will this emp IDs added to index memory  and give performance impact though i'm commiting the transaction after deleting the rows?
database : oracle 10g.
Thanks!!!

Answer 1

If I understand you correctly, this sounds like a use case for a global temporary table (with the same structure as your employee table).
As you insert, update and delete the same row within one single transaction (for the convenience of your code I assume), those row will only ever be visible to the session that (temporarily) inserts them into the table.
The design you are suggesting has (at least) the following performance impact:
1) it will inhibit concurrency
     - other sessions reading the table while transient rows are inserted and are being updated may have to clone some data buffers and apply UNDO to get read consistent clones of the buffers being modified.
     - you may cause buffer busy wait events as you modify the blocks belonging to your employee table while other sessions want to read the blocks affected by these modifications (the severity of this depends on how your 100K transactions are spread throughout the day and what activity runs on the database in parallel).
     - you will increase activity on the hash chain latches protecting the buffers of your employee table (the same applies to the severity as for the previous point).
2) You increase the amount of REDO generated by your code. Using a global temporary table your 100K transactions will also generate some REDO, but significantly less.
3) Using the global temporary table approach you don't need to delete the rows once you are done with your processing - you simply define your global temporary table as "ON COMMIT DELETE ROWS".
4) You'll have to do all the work associated with the index maintenance to insert and delete the corresponding index entry (see my post from  Jun 24, 2013 8:16 PM)