已索引

GCS (Global Cache Service) 是具体执行 Oracle RAC Cache Fusion 工作的服务。其对应的后台进程是 LMSn。

11gR2 官方文档对 LMS 进程的描述如下：

LMS: Global Cache Service Process
The LMS process maintains records of the data file statuses and each cached block by recording information in a Global Resource Directory (GRD). The LMS process also controls the flow of messages to remote instances and manages global data block access and transmits block images between the buffer caches of different instances. This processing is part of the Cache Fusion feature.

而在 Oracle 9iR2 官方文档中这样介绍：
Lock Manager Server Process (LMS)
In Oracle9i Real Application Clusters, a Lock Manager Server process (LMS) provides inter-instance resource management.
也就是说LMS进程也就是 Lock Manager Server Process 的缩写，意思是锁管理服务器进程。

了解了这些概念，有助于查看 alert 文件中的相关报错，例如：
ORA-29770: global enqueue process LMS1 (OSID 44546) is hung for more than 70 seconds
ORA-29770: global enqueue process LMS2 (OSID 44550) is hung for more than 70 seconds
ORA-29770: global enqueue process LMS3 (OSID 44554) is hung for more than 70 seconds