Database Reference
In-Depth Information
DBRM: Database ResourceManager Process
This process implements the resource plans that may be configured for a database instance. It sets the resource plans
in place and performs various operations related to enforcing/implementing those resource plans. The resource
manager allows the administrators of a database to have fine grained control over the resources used by the database
instance, by applications accessing the database, or by individual users accessing the database.
GEN0: General Task Execution Process
This process provides, as expected by its name, a general task execution thread for the database. The main goal of this
process is to offload potentially blocking processing (processing that would cause a process to stop while it occurs) from
some other process and perform it in the background. For example, if the main ASM process needs to perform some
blocking file operation, but that operation could safely be done in the background (ASM can safely continue processing
before the operation completes), then the ASM process may request the
GEN0
process to perform this operation and let
GEN0
notify it upon completion. It is similar in nature to the slave processes described further later in this chapter.
Remaining Common Focused Processes
Depending on the features of Oracle you are using, other focused processes may be visible. Some are listed here with
a brief description of their function.
■
appendix F (Background processes) of the Oracle Database reference manual, available on
http://otn.oracle.com/
, has a complete listing of the background processes and their functions.
Note
Most of the processes described previously are nonnegotiable—you will have them if you have an Oracle instance
running. (
ARCn
is technically optional but is, in my opinion, mandatory for all production databases!) The following
processes are optional and will appear only if you make use of the specific feature. The following processes are unique
to a database instance using ASM, as discussed in Chapter 3:
•
Automatic Storage Management Background
(
ASMB
)
process
: The
ASMB
process runs in a
database instance that is making use of ASM. It is responsible for communicating to the ASM
instance that is managing the storage, providing updated statistics to the ASM instance, and
providing a heartbeat to the ASM instance, letting it know that it is still alive and functioning.
•
ReBALance
(
RBAL
)
process
: The
RBAL
process also runs in a database instance that is making
use of ASM. It is responsible for processing a rebalance request (a redistribution request) as
disks are added/removed to and from an ASM disk group.
The following processes are found in an Oracle RAC instance. RAC is a configuration of Oracle whereby multiple
instances, each running on a separate node (typically a separate physical computer) in a cluster, may mount and open
a single database. It gives you the ability to have more than one instance accessing, in a full read-write fashion,
a single set of database files. The primary goals of RAC are twofold:
•
High availability
: With Oracle RAC, if one node/computer in the cluster fails due to a software,
hardware, or human error, the other nodes may continue to function. The database will be
accessible via the other nodes. You might lose some computing power, but you won't lose
access to the database.
