Following is the process to update or insert data in the database:
i. RDBMS searches for parsed statement in library cache or parses the statement to generate execution plan.
ii. Server process retrieves relevant data from disk to the buffer cache. In case of inserting data in the database, the data block with sufficient free space will be retrieved.
iii. Lock is acquired. The data block is updated in the buffer cache.
iv. A lock is acquired on rollback segment as well to store old version of data in case rollback is required.
v. User process creates a redo entry in the redo log buffer to support recovery.