oracle-undo tablespaces

which background process开发者_开发百科 helps in writing the undo data to undo tablespace /system tablespace?

Sounds like a trick question. I do not think there is (or can be) such a process. Every server process has to write undo information by itself as it updates the database blocks in the buffer cache. This cannot be deferred to a background operation.

There are background processes that write dirty blocks from the buffer cache to disk (DBWn) and from the REDO buffer to the redo logs (LGWR). What DBWn do does include updating the undo tablespace, so maybe this is what the question is about.

Usually the data will be written back from db_buffer to the respective data file (By DBWR). In the case of undo tablespace undo data from which buffer writes to undo datafile(undo tbs)?