### How to check data guard is in sync?
On Standby:
SQL> col CURRENT_SCN for 9999999999999999999
SQL> SELECT SCN_TO_TIMESTAMP(CURRENT_SCN) SYNC_UNTIL FROM V$DATABASE;
SYNC_UNTIL
---------------------------------
26-MAY-13 02.00.38.000000000 PM
SQL>
Data Guard - How To Check Whether Physical Standby is in Sync with the Primary or Not?
Summary:
1. Check for GAP on standby
2. Check redo received on standby
3. Check redo applied on standby
4. Identify missing archive log files
5. Copy archive log files
6. Register archive log files with standby
7. Restart the managed recovery operations
step 1. Check for GAP on standby
-----------------------------------------------------------------------------------------------primary + standby > select max(sequence#) from v$log_history;
primary > SELECT THREAD# "Thread",SEQUENCE# "Last Sequence Generated"
FROM V$ARCHIVED_LOG
WHERE (THREAD#,FIRST_TIME ) IN (SELECT THREAD#,MAX(FIRST_TIME) FROM V$ARCHIVED_LOG GROUP BY THREAD#)
ORDER BY 1;
-----------------------------------------------------------------------------------------------
step 2 and 3. Check redo received on standby and Check redo applied on standby
-----------------------------------------------------------------------------------------------standby > SELECT ARCH.THREAD# "Thread", ARCH.SEQUENCE# "Last Sequence Received", APPL.SEQUENCE# "Last Sequence Applied", (ARCH.SEQUENCE# - APPL.SEQUENCE#) "Difference"
FROM
(SELECT THREAD# ,SEQUENCE# FROM V$ARCHIVED_LOG WHERE (THREAD#,FIRST_TIME ) IN (SELECT THREAD#,MAX(FIRST_TIME) FROM V$ARCHIVED_LOG GROUP BY THREAD#)) ARCH,
(SELECT THREAD# ,SEQUENCE# FROM V$LOG_HISTORY WHERE (THREAD#,FIRST_TIME ) IN (SELECT THREAD#,MAX(FIRST_TIME) FROM V$LOG_HISTORY GROUP BY THREAD#)) APPL
WHERE
ARCH.THREAD# = APPL.THREAD#
ORDER BY 1;
-----------------------------------------------------------------------------------------------
step 4. Identify missing archive log files
------------------------------------------------------------------------------------------------- if GAP
standby > SELECT THREAD#, LOW_SEQUENCE#, HIGH_SEQUENCE# FROM V$ARCHIVE_GAP;
-----------------------------------------------------------------------------------------------
step 5. Copy archive log files
-----------------------------------------------------------------------------------------------After identifying a gap (as shown above), the DBA will need to query the primary database
to locate the archived redo logs on the primary database. The following query assumes the
local archive destination on the primary database is LOG_ARCHIVE_DEST_1:
primary > SELECT name
FROM v$archived_log
WHERE thread# = 1
AND dest_id = 1
AND sequence# BETWEEN 09464 and 90468;
-----------------------------------------------------------------------------------------------
step 6. Register archive log files with standby
------------------------------------------------------------------------------------------------- Copy the above redo log files to the physical standby database and register
them using the ALTER DATABASE REGISTER LOGFILE ... SQL statement on the
physical standby database.
For example:
standby > ALTER DATABASE REGISTER LOGFILE '/u04/arch/HSBC33/arch_t1_s64.dbf';
standby > ALTER DATABASE REGISTER LOGFILE '/u04/arch/HSBC33/arch_t1_s65.dbf';
standby > ALTER DATABASE REGISTER LOGFILE '/u04/arch/HSBC33/arch_t1_s66.dbf';
standby > ALTER DATABASE REGISTER LOGFILE '/u04/arch/HSBC33/arch_t1_s67.dbf';
standby > ALTER DATABASE REGISTER LOGFILE '/u04/arch/HSBC33/arch_t1_s68.dbf';
-----------------------------------------------------------------------------------------------
step 7. Restart the managed recovery operations
------------------------------------------------------------------------------------------------- After the redo logs have been registered on the physical standby database,
the DBA can restart the managed recovery operations.
For example, to put the physical standby database into automatic recovery managed mode:
standby > alter database recover managed standby database disconnect from session;
-----------------------------------------------------------------------------------------------
