ocr和votedisk是什么？

作为集群，oracle cluster需要共享存储来存放整个集群的配置信息，ocr便是用例存放这些配置信息的地方，ocr的存储容量一般不会太大，在10g下，oracle建议256M已经足以。ocr必须需要存储在集群文件系统或者裸设备上，出于性能上的考虑，本人建议将ocr建立在裸设备上，性能高并且管理也不复杂（ocr和votedisk的数量一般不会太多）。ocr中存放的是集群的配置信息，这些信息只能在一个节点上进行维护操作，这一节点叫做Master Node，其他节点会在内存中保留一份ocr的复制，并且只能进行读操作，所有ocr的更新都是有master node来执行并通知各个节点的。

votedisk磁盘存储集中地各个节点并用来进行心跳监测

ocr和votedisk的维护是否需要保持脱机状态？

orc的维护在大多数情况下，是需要联机操作的，因为在各个节点具有ocr.loc文件，联机操作可以保证各个节点的ocr.loc文件及时得到更新。但是部分操作，如repaire和重建等操作需要在脱机状态下进行（后面会详细描述）

votedisk磁盘的维护往往需要在脱机状态下进行

ocr维护的命令有哪些？

维护ocr常用的命令有：

ocrcheck

[root@node1 bin]# ./ocrcheck -h
Name:
	ocrcheck - Displays health of Oracle Cluster Registry.

Synopsis:
	ocrcheck 

Description:
	prompt> ocrcheck
	Displays current usage, location and health of the cluster registry

Notes:
	A log file will be created in
	$ORACLE_HOME/log//client/ocrcheck_.log. Please ensure
	you have file creation privileges in the above directory before
	running this tool.

[root@node1 bin]# ./ocrdump -h
Name:
	ocrdump - Dump contents of Oracle Cluster Registry to a file.

Synopsis:
	ocrdump [|-stdout] [-backupfile ] [-keyname ] [-xml] [-noheader]

Description:
	Default filename is OCRDUMPFILE. Examples are:

	prompt> ocrdump
	writes cluster registry contents to OCRDUMPFILE in the current directory

	prompt> ocrdump MYFILE
	writes cluster registry contents to MYFILE in the current directory

	prompt> ocrdump -stdout -keyname SYSTEM
	writes the subtree of SYSTEM in the cluster registry to stdout

	prompt> ocrdump -stdout -xml
	writes cluster registry contents to stdout in xml format

Notes:
	The header information will be retrieved based on best effort basis.
	A log file will be created in
	$ORACLE_HOME/log//client/ocrdump_.log. Make sure
	you have file creation privileges in the above directory before
	running this tool.

[root@node1 bin]# ./ocrconfig -h
Name:
	ocrconfig - Configuration tool for Oracle Cluster Registry.

Synopsis:
	ocrconfig [option]
	option:
		-export  [-s online]
		                                    - Export cluster register contents to a file
		-import                   - Import cluster registry contents from a file
		-upgrade [ []]
		                                    - Upgrade cluster registry from previous version
		-downgrade [-version ]
		                                    - Downgrade cluster registry to the specified version
		-backuploc                 - Configure periodic backup location
		-showbackup                         - Show backup information
		-restore                  - Restore from physical backup
		-replace ocr|ocrmirror [] - Add/replace/remove a OCR device/file
		-overwrite                          - Overwrite OCR configuration on disk
		-repair ocr|ocrmirror     - Repair local OCR configuration
		-help                               - Print out this help information

Note:
	A log file will be created in
	$ORACLE_HOME/log//client/ocrconfig_.log. Please ensure
	you have file creation privileges in the above directory before
	running this tool.?

Table D-1 The ocrconfig Command Options