In Oracle® Clusterware Administration and Deployment Guide 11g Release 2 (11.2), the section, Diagnostics Collection Script, says that:
Every time an Oracle Clusterware error occurs, run the diagcollection.pl script to collect diagnostic information from Oracle Clusterware in trace files. The diagnostics provide additional information so Oracle Support can resolve problems. Run this script from the following location:
Grid_home/bin/diagcollection.pl
Note:
You must run this script as the root user.