Oracle Processes - Expert Oracle Database Architecture - page 199

CTWR: Change Tracking Processes
This is an optional process starting with Oracle 10 g database and above. The CTWR process is responsible for
maintaining the change tracking file, as described in Chapter 3.
RVWR: Recovery Writer
This process (available with Oracle 10 g database and above), is responsible for maintaining the before images of
blocks in the Fast Recovery Area (described in Chapter 3) used with the FLASHBACK DATABASE command.
DMnn/DWnn: Data Pump Master/Worker Processes
Data Pump was a feature added in Oracle 10 g Release 1 of the database. It was designed as a complete rewrite of
the legacy export/import processes. Data Pump runs entirely in the server and the API to it is via PL/SQL. Since
Data Pump runs in the server, support for performing the various Data Pump operations were added. The Data
Pump master ( DMnn ) collects all inputs from client processes (it is the process that receives the API inputs) and
then coordinates the worker processes (the DWnn ) which perform the real work—the DMnn processes do the actual
processing of the metadata and data.
TMON/TT00: Transport Monitor and Redo Transport Slave
Starting with Oracle 12 c , two Data Guard related processes are automatically started when your instance starts: a
transport monitor process ( TMON ) and a redo transport slave ( TT00 ). TMON will start and monitor a number of TT00
processes. The TT00 processes are used to inform the LGWR process if and when it needs to generate heartbeat redo.
Even if you don't implement Data Guard, you may see the processes started. You don't need to worry about these
processes, just be aware that they're there and will be used if you implement Data Guard.
If you do implement Data Guard, there will be a number of other processes started to facilitate the shipping
of redo information from one database to another, and apply it. See the Data Guard Concepts and Administration
manual from Oracle for full details.
Remaining Utility Background Processes
So, is that the complete list? No, not by a long shot, there are many others depending on what features you
implemented. For example, there are Streams apply and capture processes present when you implement products
such as Oracle GoldenGate, Oracle XStream, Oracle Streams, and so on. However, the preceding list covers most of
the common background processes you will encounter.
Slave Processes
Now we are ready to look at the last class of Oracle processes: the slave processes. There are two types of slave
processes with Oracle, I/O slaves and parallel query slaves.