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§ Architecture:-
Ø Primary
database – It refers to the production database.
Ø Standby
database – It refers to a copy of primary/Production database. Data guard
architecture must have at least one or more than one standby database.
Ø Log
transport service –It manages transfer of archive log files from primary to
standby database.
Ø Network configuration – It refers to the network connection between primary and standby database. This connection is based on Oracle Net.
Ø Log
apply services – It applies archived logs to the standby database.
Ø Role
management services – It manages the role change between primary and standby
database.
Ø Data
guard broker – It manages data guard creation process and monitors the data guard.
Ø Maximum Protection Mode:
It specifies that a data change on primary Database is acknowledged only when it is available to standby database at least in the form of redo log information.In this mode, primary database shuts down if at least one standby database cannot be updated.So in MAXIMUM PROTECTION mode, user don't get a commit acknowledgment until transactions are successfully written to at least one standby destination.
Redo
Archival Process: LGWR
Network
Transmission mode: SYNC
Disk
Write Option: AFFIRM
Standby
Redo Logs: Yes
Standby
Database Type: Physical standby database And Logical standby database.
Ø Maximum Availability Mode:
Unlike maximum protection mode, the primary database
will not shut down if a fault prevents it from writing its redo stream to a synchronized standby database. Instead, the primary
database will operate in RESYNCHRONIZATION until the fault is corrected and all log gaps have been resolved. When all log gaps
have been resolved, the primary database automatically resumes operating in maximum availability mode.
Redo
Archival Process: LGWR
Network
Transmission mode: SYNC
Disk
Write Option:
Standby
Redo Logs: Yes
Standby
Database Type: Physical standby database, Logical standby database and Snapshot
standby database.
Ø Maximum Performance Mode:
Redo
Archival Process: LGWR or ARCH (ARCH is not recommended)
Network
Transmission mode: ASYNC
Disk
Write Option: NO AFFIRM
Standby
Redo Logs: NO (But it is recommended for Real-Time Apply)
Standby
Database Type: Physical standby database, Logical standby database and Snapshot
standby database.
Ø Fetch Archive Log (FAL) –
Standby database requires Fetch Archive Log (FAL) client to request and fetch
archive log files from primary database.
Ø Remote File Server (RFS) – RFS to
receive archived log files from primary
database,
Ø Archiver process –
It is used to archive redo logs applied to standby database.
Ø Managed Recovery Process (MRP) – MRP is
used to apply redo logs to the
standby database.
§ Role Transition:
v Role Transition is the change of role
between primary and standby database.
It can happen in the following two cases:
Ø Switchover
– When primary database is switched to standby database and standby database is
switched to primary database (Vice-Versa).
Ø
Failover – Where Standby database can
be used as a disaster recover solution in case of a failure in the primary
database.
§ Changing the Data Guard Protection Mode:
By default
protection mode is MAXIMUM PERFORMANCE. So we will change it to MAXIMUM
PROTECTION Mode. But we have to make Primary database in mount stage to change the existing protection mode.
The
data protection mode can be set to MAXIMUM PROTECTION on an open database only if the current data protection
mode is MAXIMUM AVAILABILITY and if there is at least one synchronized standby
database.
[oracle@PRODDB~]$ sqlplus / as sysdba
SQL*Plus:
Release 19.0.0.0.0 - Production on Wed May 12 01:05:27 2021
Version 19.3.0.0.0
Copyright (c) 1982, 2019, Oracle. All rights reserved.
Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0
SQL> select name,db_unique_name,open_mode,database_role,protection_mode from v$database;
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
3 PRODDB_PDB READ WRITE NO
SQL> show parameter log_archive_dest_2 |
NAME |
TYPE |
VALUE |
|
log_archive_dest_2 |
string |
service=PRODDR NOAFFIRM LGWR ASYNC VALID_FOR=(ALL_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=PRODDR |
SQL> shut immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.
SQL> ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE {AVAILABILITY | PERFORMANCE | PROTECTION};
SQL> ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE PROTECTION;
Database altered.SQL> ALTER SYSTEM SET LOG_ARCHIVE_DEST_2='SERVICE=PRODDR AFFIRM LGWR SYNC VALID_FOR=(ALL_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=PRODDR' scope=both;
SQL> show parameter log_archive_dest_2
|
NAME |
TYPE |
VALUE |
|
log_archive_dest_2 |
string |
service=PRODDR AFFIRM LGWR SYNC VALID_FOR=(ALL_LOGFILES,PRIMARY_ROLE)
DB_UNIQUE_NAME=PRODDR |
SQL> alter database open;
Database altered.
SQL> select
name,db_unique_name,open_mode,database_role,protection_mode from v$database.
|
NAME |
DB_UNIQUE_NAME |
OPEN_MODE |
DATABASE_ROLE |
PROTECTION_MODE |
|
PRODDB |
PRODDB |
READ WRITE |
PRIMARY |
MAXIMUM PERFORMANCE |
