Here is the brief explanation that how the clusterware brings up step by step . 1. When a node of an Oracle Clusterware cluster start/restarts, OHASD is started by platform-specific means. OHASD is the root for bringing up Oracle Clusterware. OHASD has access to the OLR (Oracle Local Registry) stored on the local file system. … Continue reading RAC : 11gR2 Clusterware Startup Sequence