In a MOM failover configuration, especially supported Windows platforms, how must the filesystem links to shared directories be established?

Document ID : KB000044582
Last Modified Date : 14/02/2018
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 Introduction: 

 When setting up primary and secondary MOM Enterprise Managers in a failover configuration, it is necessary to relocate a single copy of certain directories from the root of the EM installation tree to shared storage (high-performance SAN or NAS) that both primary and secondary MOM processes have read/write access. 

 The primary and secondary MOM are then configured with filesystem links to these shared directories so that each MOM sees the same shared directories within their own individual EM installation tree.  On Windows systems, these links must be made to UNC target paths.

 

 Question:

 In a MOM failover configuration specifically on supported Windows platforms, how must the filesystem links to shared directories be established?

 

 Environment:  

 Windows platforms supported for Introscope Enterprise Manager

 

 Answer: 

 On Windows platforms, filesystem links (“symbolic links”) are made using the MKLINK command-line utility.  MKLINK can create symbolic links to directories specifically, designated by a /D option to the utility.  Directory symbolic links, and thus the /D option, are needed when creating the links on primary and secondary MOM for each of the shared directories on the SAN or NAS device.

 

 The general form of the MKLINK command will be:

 

MKLINK /D LINK TARGET

 

 where TARGET is the UNC path to the shared directory on SAN/NAS, and LINK is the name of the link to create within the root of the primary or secondary MOM’s installation tree.  The name of this link must be the same as the basename of the directory given by the UNC path.

 

 For example: one such EM directory that is shared in a failover configuration is the config directory.  Let’s assume this config directory resides at UNC path

 \\san-server\mom-failover\config

 

 On the primary and secondary MOM you must link this directory into the root of their EM installation tree. Enter something like the following at the Command Prompt:

 

cd \path\to\EM_HOME\

MKLINK /D config \\san-server\mom-failover\config

 

 It is critical to note that the target path to the MKLINK command must NOT reside at a drive letter.  The Enterprise Manager will fail to start.  The target path MUST be a UNC path.

 

 

 Additional Information:

 Also see this document on the CA APM Communities which details the MOM failover configuration:

 https://communities.ca.com/docs/DOC-231168340