ORACLE - Data Guard - STARTUP - MOUNT - OPEN READ ONLY

Let check the different scenarios to open a data guard:
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1. STARTUP will open with READ ONLY WITH APPLY
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SQL> shutdown immediate
ORA-01109: database not open

Database dismounted.
ORACLE instance shut down.
SQL> STARTUP
ORACLE instance started.
Total System Global Area 1043886080 bytes
Fixed Size                  2234960 bytes
Variable Size             729810352 bytes
Database Buffers          306184192 bytes
Redo Buffers                5656576 bytes
Database mounted.
Database opened.

SQL> SELECT OPEN_MODE, PROTECTION_MODE, PROTECTION_LEVEL, DATABASE_ROLE ROLE FROM V$DATABASE;
OPEN_MODE            PROTECTION_MODE      PROTECTION_LEVEL     ROLE
-------------------- -------------------- -------------------- ----------------
READ ONLY WITH APPLY MAXIMUM PERFORMANCE  MAXIMUM PERFORMANCE  PHYSICAL STANDBY

Note: It will take few seconds to change status from READ ONLY to READ ONLY WITH STANDBY

SQL>select * from jtable;
1000

Using DGMGRL:
DGMGRL> show database verbose 'ATEST_STBY';
Database - ATEST_STBY
  Role:            PHYSICAL STANDBY
  Intended State:  APPLY-ON
  Transport Lag:   0 seconds
  Apply Lag:       0 seconds
  Real Time Query: ON
  Instance(s):   ATEST

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2. STARTUP MOUNT will open with MOUNTED and REDO APPLY ON
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SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.
Total System Global Area 1043886080 bytes
Fixed Size                  2234960 bytes
Variable Size             729810352 bytes
Database Buffers          306184192 bytes
Redo Buffers                5656576 bytes
Database mounted.

SQL> SELECT OPEN_MODE, PROTECTION_MODE, PROTECTION_LEVEL, DATABASE_ROLE ROLE FROM V$DATABASE;
OPEN_MODE            PROTECTION_MODE      PROTECTION_LEVEL     ROLE
-------------------- -------------------- -------------------- ----------------
MOUNTED              MAXIMUM PERFORMANCE  MAXIMUM PERFORMANCE  PHYSICAL STANDBY

SQL> select * from jtable2;
select * from jtable
              *
ERROR at line 1:
ORA-01219: database not open: queries allowed on fixed tables/views only
Using DGMGRL:

DGMGRL> show database verbose 'ATEST_STBY';
Database - ATEST_STBY
  Role:            PHYSICAL STANDBY
  Intended State:  APPLY-ON
  Transport Lag:   0 seconds
  Apply Lag:       0 seconds
  Real Time Query: OFF
  Instance(s):    ATEST

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3. Oracle 11gR2 : alter database open read only will make DG READONLY with REDO APPLY
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SQL>  alter database open read only;
Database altered.

SQL> SELECT OPEN_MODE, PROTECTION_MODE, PROTECTION_LEVEL, DATABASE_ROLE ROLE FROM V$DATABASE;
OPEN_MODE            PROTECTION_MODE      PROTECTION_LEVEL     ROLE
-------------------- -------------------- -------------------- ----------------
READ ONLY            MAXIMUM PERFORMANCE  MAXIMUM PERFORMANCE  PHYSICAL STANDBY

SQL> SELECT OPEN_MODE, PROTECTION_MODE, PROTECTION_LEVEL, DATABASE_ROLE ROLE FROM V$DATABASE;
OPEN_MODE            PROTECTION_MODE      PROTECTION_LEVEL     ROLE
-------------------- -------------------- -------------------- ----------------
READ ONLY WITH APPLY MAXIMUM PERFORMANCE  MAXIMUM PERFORMANCE  PHYSICAL STANDBY

Using DGMGRL:
show database verbose 'ATEST_STBY';
Database - ATEST_STBY
  Role:            PHYSICAL STANDBY
  Intended State:  APPLY-ON
  Transport Lag:   0 seconds
  Apply Lag:       0 seconds
  Real Time Query: ON
  Instance(s):   ATEST

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