Oracle RAC 11gR2 – ORA-01102: cannot mount database in exclusive mode
In one of the customer site, I was unable to start both of the RAC instance at the same time. When 1 of the RAC instance was up, I couldn’t start the other RAC instance.
#sqlplus / as sysdba SQL> startup; ERROR at line 1: ORA-01102: cannot mount database in EXCLUSIVE mode
ORA-01102 error occurs when 2 separate (Not RAC configured) Oracle instance tries to open the same database. In one of the RAC instance, one of the parameter was configured wrongly
CLUSTER_DATABASE = FALSE;
SQL>alter system set cluster_database=TRUE scope=spfile sid='SID1'; SQL>shutdown immediate; SQL>startup
Hope this helps.