ORA-16006: audit_trail destination incompatible with database open mode on redhat 5.2 10gr2 (10.2.0.4)

 ORA-16006: audit_trail destination incompatible with database open mode
while i was trying to open standby database got below error message

ORA-16006: audit_trail destination incompatible with database open mode

at little search on metalink found below note: ID 835638.1

solution:

SQL>alter system set audit_trail=OS scope=spfile;