Hi, } 1) alter parameter "control_files" scope=spfile to remove 1 of the control files- there will still be at least 3 left. } 2) shutdown and restart each instance of a RAC cluster one at a time, in a rolling fashion. as it has already been pointed out (this is 11gR2, not R1): SQL> show parameter control_files NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ control_files string +FRA001/rac11gr2/controlfile/c urrent.266.746893637, +DATA001 /rac11gr2/controlfile/current. 273.746893651 SQL> alter system set control_files = '+DATA001/rac11gr2/controlfile/current.273.746893651' scope = spfile; System altered. SQL> shu immediate Database closed. Database dismounted. ORACLE instance shut down. SQL> startup ORACLE instance started. Total System Global Area 535662592 bytes Fixed Size 1345376 bytes Variable Size 398461088 bytes Database Buffers 130023424 bytes Redo Buffers 5832704 bytes ORA-01105: mount is incompatible with mounts by other instances ORA-01104: number of control files (1) does not equal 2 Regards Dimitre -- //www.freelists.org/webpage/oracle-l