Oracle Background Processes

In an earlier lesson we presented a diagram identifying various components of the Oracle instance. Included in the diagram were various processes

1. DBWR,
2. SMON,
3. LGWR,
4. PMON,
5. CKPT, and

that reside inside the instance. There are also two groups of processes that reside outside the instance, and that are used to communicate from the user to the instance.

The second group is a set of processes that communicate user requests to the instance. A good analogy is Applebee's restaurant. Customers (client applications) come into the restaurant for lunch (create user processes). A server process takes the order (client data requests) and pass it on to the order taker (the instance). The cook would prepare the food (request data from the database) and let the servers know it is ready. The then takes the food (data) and presents it to the customer (client application). We will investigate the four processes that reside as part of the instance:

1. LGWR,
2. ARCH,
3. DBWR and,
4. CKPT.

Of these four processes ARCH is optional, while the other three are created during the creation of an instance. We will discuss these four processes in detail in the next four lessons. There is a V$ view that provides some information about the background and server processes, V$PROCESS. View the image below to see an example of the output from this view.

The ARCH process, also known as the Archiver process, is a background process in an Oracle database instance that is responsible for writing redo log data to disk. The redo log data contains information about changes made to the database, and is used to recover the database in the event of a failure.
The purpose of the ARCH process is to ensure that the redo log data is written to disk as quickly as possible, so that the database can be recovered in the event of a failure. The ARCH process runs in the background and continually writes the redo log data to disk, so that it can be used to recover the database.
The ARCH process is an important component of the database, as it plays a critical role in protecting the data and ensuring that the database can be recovered in the event of a failure. If the ARCH process fails or is not running, the redo log data may not be written to disk in a timely manner, and the database may not be recoverable in the event of a failure.
In general, the ARCH process should be closely monitored by a DBA to ensure that it is running correctly and that the redo log data is being written to disk in a timely manner. The DBA may also need to adjust the configuration of the ARCH process to ensure that it is running efficiently and effectively, based on the specific needs of the database and the system.

Before you move on to the next lesson, click the Quiz link below to answer some questions about instances.
Oracle Memory Structures - Quiz