In Oracle® Grid Infrastructure Installation Guide 11g Release 2 (11.2) for Linux, the section, About the Oracle Clusterware Alert Log, says that:
The Oracle Clusterware alert log is the first place to look for serious errors. In the event of an error, it can contain path information to diagnostic logs that can provide specific information about the cause of errors.
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The location of the Oracle Clusterware log file is CRS_home/log/hostname/alerthostname.log, where CRS_home is the directory in which Oracle Clusterware was installed and hostname is the host name of the local node.
In Oracle® Clusterware Administration and Deployment Guide 11g Release 2 (11.2), the section, Clusterware Log Files and the Unified Log Directory Structure, says that:
Footnote 1 The directory structure is the same for Linux, UNIX, and Windows systems.
Footnote 2 To change the amount of logging, edit the path in the Grid_home/srvm/admin/ocrlog.ini file.