update & rollback segment mechanism

Hi Gurus,

I have a question about update mechanism. How does oracle manages the buffers when multiple rows are updated by different transactions? For instance, imagine there is a database block which has recordA and recordB and the data is cached in shared memory in block1. When recordA is updated , the original block is copied into the rollback segment.Then when recordB is also updated without commiting the first transaction, does oracle creates a new block in rollback segment(or undo tablespace) or use the existing one in order to keep the original version of recordB?

Also , since the rollback segment is on disk , is there any buffer in shared memory which rollback data is cached ?

Kind Regards,
hope Received on Fri Oct 24 2003 - 06:09:27 CDT