Oracle 体系结构总体认识
先对Oracle 体系结构有个总体的认识。Oracle体系结构，我觉得，大体可分：内存结构，进程结构和存储结构。其中，进程结构是内存结
先对Oracle 体系结构有个总体的认识。Oracle体系结构，，我觉得，大体可分：内存结构，进程结构和存储结构。其中，进程结构是内存结构和存储结构的沟通桥梁。
在不同的平台上，oracle体系结构的实现略有不同。比如，在unix（linux）上，实现为多进程；在windows上，实现为多线程。一般不建议把oracle部署在windows上哈。因为，win的单进程体系结构使oracle服务器最多只有2G的内存使用量。
既然提到oracle服务器了，就来唠叨一下它的组成吧。oracle server由oracle instance和oracle database组成。实例由SGA（内存空间）和后台进程构成；数据库由磁盘上的文件集组成。他们两人的关系是：实例终其一生也只能mount并open一个数据库；而一个数据库可以被一个或多个实例mount and open。通常，我们会说“数据库up，数据库down”，其实，本质上是“实例up，实例down”。一夫多妻呀。数据库是老公，实例是老婆。封建时代，老公有多个老婆，叫正常；老婆有多个老公，啊啊。。，接受不鸟哈。
有图有真相哈：
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