What is Standard Edition RAC?
With Oracle Database 10g, a customer who has purchased Standard Edition is allowed to use the RAC option within the limitations of Standard Edition(SE). For licensing restrictions you should read the Oracle Database 10g License Doc. At a high level this means that you can have a max of 4 cpus in the cluster, you must use ASM for all database files. Oracle Cluster File System (OCFS) is not supported for use with SE RAC. NOTE: OCFS2 is not supported for any database related files with SE RAC.