SQL> select open_mode from v$database;
OPEN_MODE
MOUNTED
SQL> shutdown immediate;
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
SQL> startup;
ORACLE instance started.
Total System Global Area 1.1124E+10 bytes
Fixed Size 2229560 bytes
Variable Size 5670701768 bytes
Database Buffers 5435817984 bytes
Redo Buffers 14983168 bytes
Database mounted.
Database opened.
SQL> select open_mode from v$database;
OPEN_MODE
READ ONLY
SQL> alter database recover managed standby database disconnect from session;
Database altered.
SQL> SELECT PROCESS, STATUS, THREAD#, SEQUENCE#, BLOCK#, BLOCKS FROM V$MANAGED_STANDBY;
PROCESS STATUS THREAD# SEQUENCE# BLOCK# BLOCKS
ARCH CLOSING 1 23 1 71
ARCH CONNECTED 0 0 0 0
ARCH CONNECTED 0 0 0 0
ARCH CLOSING 1 21 1 568
MRP0 WAIT_FOR_LOG 1 24 0 0
RFS IDLE 0 0 0 0
RFS IDLE 0 0 0 0
RFS IDLE 0 0 0 0
RFS IDLE 1 24 91 1
http://gavinsoorma.com/2010/09/11g-active-data-guard-enabling-real-time-query/