Database Reference
In-Depth Information
You can use features such as the Advanced Queuing (AQ) to turn a long-running process into an apparently short
one, but you have to
design
that into your application. These sorts of things are best done when you are developing.
Also, historically, there have been differences between the feature set available to shared server connections versus
dedicated server connections. We already discussed the lack of automatic PGA memory management in Oracle9
i
,
for example, but also in the past, things as basic as a hash join between two tables were not available in shared server
connections. (Hash joins are available in the current 9
i
and above releases with shared server!)
Background Processes
The Oracle instance is made up of two things: the SGA and a set of background processes. The background processes
perform the mundane maintenance tasks needed to keep the database running. For example, there is a process that
maintains the block buffer cache for us, writing blocks out to the data files as needed. Another process is responsible
for copying an online redo log file to an archive destination as it fills up. Yet another process is responsible for cleaning
up after aborted processes, and so on. Each of these processes is pretty focused on its job, but works in concert with all
of the others. For example, when the process responsible for writing to the log files fills one log and goes to the next, it
will notify the process responsible for archiving that full log file that there is work to be done.
There is a
V$
view you can use to see all of the
possible
Oracle background processes and determine which ones
are in use in your system currently:
EODA@ORA12CR1> select paddr, name, description
2 from v$bgprocess
3 order by paddr desc
4 /
PADDR NAME DESCRIPTION
---------------- ---- ----------------------------------------
0000000072FD44C8 MMON Manageability Monitor Process
00000000727FD850 MMNL Manageability Monitor Process 2
00000000723FE138 LREG Listener Registration
00000000723FCFD8 SMON System Monitor Process
00000000723F9BB8 CKPT checkpoint
00000000723F8A58 LGWR Redo etc.
00000000723F78F8 DBW0 db writer process 0
...
00 VMB0 Volume Membership 0
00 ACFS ACFS CSS
00 SCRB ASM Scrubbing Master
00 XDMG cell automation manager
00 XDWK cell automation worker actions
401 rows selected.
Rows in this view with a
PADDR
other than 00 are processes (threads) configured and running on your system.
■
Tip
another way to view currently running background processes is to query
V$PROCESS
where
PNAME
is not null.
