Overview of Oracle Processes
This section describes the two types of processes that run the Oracle database server
code (server processes and background processes). It also describes the trace files and
alert logs, which record database events for the Oracle processes.
ORACLE进程概述
这部份描述两种类型的进程ORACLE的服务代码（服务进程和后台进程）。也描述了跟踪
日志文件和ALERT日志，它们记录了ORACLE进程的数据库事件
Server Processes
Oracle creates server processes to handle the requests of user processes connected to
the instance. In some situations when the application and Oracle operate on the same
computer, it is possible to combine the user process and corresponding server process
into a single process to reduce system overhead. However, when the application and
Oracle operate on different computers, a user process always communicates with
Oracle through a separate server process.
服务进程
ORACLE创建服务进程去处理连接实例用户进程的请求，在一些时候当应用和ORACLE操作在
同一台电脑时，它可能去合并用户进程和对应的服务进程为一个单独进程而减少系统的负载。
但当应用和ORACLE操作在不同电脑时，一个用户进程通常连接ORACLE通过一个单独的服务进程。
Server processes (or the server portion of combined user/server processes) created on
behalf of each user’s application can perform one or more of the following:
服务进程(或一些用户/服务进程部份)创建好处对于每个用户的应用可以执行一个或更多如下：
■ Parse and run SQL statements issued through the application
■ Read necessary data blocks from datafiles on disk into the shared database buffers
of the SGA, if the blocks are not already present in the SGA
■ Return results in such a way that the application can process the information
Background Processes
To maximize performance and accommodate many users, a multiprocess Oracle
system uses some additional Oracle processes called background processes.
An Oracle instance can have many background processes; not all are always present.
There are numerous background processes. See the V$BGPROCESS view for more
information on the background processes. The background processes in an Oracle
instance can include the following:
解析和运行SQL语句输入通过应用
读取需要的数据块从磁盘中的数据文件到共享数据库缓冲池在SGA中的，如果块没有出
现在SGA中.
以应用可以处理的信息这种方式返回结果
#后台进程
■ Database Writer Process (DBWn) --数据库写入进程
■ Log Writer Process (LGWR) --日志写入进程
■ Checkpoint Process (CKPT) --检查点进程
■ System Monitor Process (SMON) --系统监控进程
■ Process Monitor Process (PMON) --进程监控进程
■ Recoverer Process (RECO) --恢复进程
■ Job Queue Processes --任务对列进程
■ Archiver Processes (ARCn) --归档进程
■ Queue Monitor Processes (QMNn) 对象监控进程
■ Other Background Processes --其它后台进程
On many operating systems, background processes are created automatically when an
instance is started.
在非常多的操作系统中，当一个实例启动后后台进程被自动创建的。
