Exception handling in PLSQL

Hi,

 I am trying to write a Stored procedure which will delete the contents of a table(>3000000 records) at a time. I have implememted logic to break down the records into sizable chunks and then delete. But still intermittently I get ORA-30036: unable to extend segment by 8 in undo tablespace 'UNDOTBS1'  while running the Stored proceedure. Please let me know how to handle this in the SP and capture the error code and desc.

Also is there any way to handle general runtime exceptions and capture the error code and desc. I have 2 out params which is meant to send back the error code and desc.