ORA-39700: database must be opened with UPGRADE option when upgrading standby instance

You might see error “ORA-39700: database must be opened with UPGRADE option “  in standby instance after Oracle version upgrade even if standby binary is also upgraded to same version as of primary

[oracle@admdbbk001:/orasw/app/oracle/product/11.2.0.4/db]# echo $ORACLE_HOME

/orasw/app/oracle/product/11.2.0.4/db

[oracle@admdbbk001:/orasw/app/oracle/product/11.2.0.4/db]# sqlplus '/ as sysdba'

SQL*Plus: Release 11.2.0.4.0 Production on Mon Mar 9 10:14:01 2015

Copyright (c) 1982, 2013, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> startup

ORACLE instance started.

Total System Global Area 2137886720 bytes

Fixed Size                  2248080 bytes

Variable Size             822084208 bytes

Database Buffers         1291845632 bytes

Redo Buffers               21708800 bytes

Database mounted.

ORA-01092: ORACLE instance terminated. Disconnection forced

ORA-00704: bootstrap process failure

ORA-39700: database must be opened with UPGRADE option

Process ID: 17039506

Session ID: 588 Serial number: 3

Fix is to start standby instance in mount mode, start listener and wait for logs to be transferred and applied to standby.

SQL> startup mount;

ORACLE instance started.

Total System Global Area 2137886720 bytes

Fixed Size                  2248080 bytes

Variable Size             822084208 bytes

Database Buffers         1291845632 bytes

Redo Buffers               21708800 bytes

Database mounted.

SQL> alter database recover managed standby database using current logfile disconnect;

Database altered.

SQL> select name,open_mode,database_role,switchover_status from v$database;

NAME      OPEN_MODE            DATABASE_ROLE    SWITCHOVER_STATUS

--------- -------------------- ---------------- --------------------

TEST11G   MOUNTED              PHYSICAL STANDBY NOT ALLOWED

After few minutes once it has applied all logs, we can shutdown and start database and error will disappear.