DR Iq
DR Iq
DR Iq
High Availability.
Data Protection.
Role -Transitions.
What are the different Protection modes available in Oracle Data Guard?
Below are the protection modes available in DG
1. Maximum Protection
2. Maximum Availability
3. Maximum Performance => This is the default protection mode. It provides the highest level of
data protection that is possible without affecting the performance of a primary database. This is
accomplished by allowing transactions to commit as soon as all redo data generated by those
transactions has been written to the online log.
How to check what protection mode of primary database in your Oracle Data
Guard?
SELECT PROTECTION_MODE FROM V$DATABASE;
How to change protection mode in Oracle Data Guard setup?
ALTER DATABASE SET STANDBY DATABASE TO MAXIMUM [PROTECTION |
PERFORMANCE | AVAILABILITY];
What are the advantages of using a Physical standby database in Oracle Data
Guard?
1. High Availability.
2. Load balancing (Backup and Reporting).
3. Data Protection.
4. Disaster Recovery.
1. Log Writer Process (LGWR): Collects redo information and updates the online redo logs. It can
also create local archived redo logs and transmit online redo to standby databases.
2. Archiver Process (ARCn): One or more archiver processes make copies of online redo logs
either locally or remotely for standby databases.
3. Fetch Archive Log (FAL) Server: Services requests for archive redo logs from FAL clients
running on multiple standby databases. Multiple FAL servers can be run on a primary database,
one for each FAL request.
4. Log network server (LNS): LNS is used on the primary to initiate a connection with the standby
database.
1. Fetch Archive Log (FAL) Client: Pulls archived redo log files from the primary site. Initiates
transfer of archived redo logs when it detects a gap sequence.
2. Remote File Server (RFS): Receives archived and/or standby redo logs from the primary
database.
3. Archiver (ARCn) Processes: Archives the standby redo logs applied by the managed recovery
process (MRP).
4. Managed Recovery Process (MRP): pplies archive redo log information to the standby database.
It controls the automated transfer of redo data from the production database to one or
more archival destinations. The redo transport services perform the following tasks:
What is RTS (Redo Transport Services) in Data-guard?
Transmit redo data from the primary system to the standby systems in the configuration.
Manage the process of resolving any gaps in the archived redo log files due to a network
failure.
Automatically detect missing or corrupted archived redo log files on a standby system and
automatically retrieve replacement archived redo log files from the primary database or
another standby database.
Control the automated transfer of redo data from a database destination to one or more
destinations. Redo transport services also manage the process of resolving any gaps in
the archived redo log files due to a network failure.
How to delay the application of logs to a physical standby?
A standby database automatically applies redo logs when they arrive from the primary
database. But in some cases, we want to create a time lag between the archiving of a
redo log at the primary site, and the application of the log at the standby site.
Modify the Log_Archive_Dest_n initialization parameter on the primary database to set a
delay for the standby database.
Example: For 60min Delay:
ALTER SYSTEM SET LOG_ARCHIVE_DEST_2=’SERVICE=stdby_srvc DELAY=60′;
The DELAY attribute is expressed in minutes.
The archived redo logs are still automatically copied from the primary site to the standby
site, but the logs are not immediately applied to the standby database. The logs are
applied when the specified time interval expires.
Physical block corruptions are repaired automatically either at primary or physical standby
database.
RMAN backups can be initiated from standby , instead of primary which will reduce cpu load
from primary.
What is active dataguard duplicate?
Starting from 11g we can duplicate database by two way 1) Active DB duplicate 2) Backup-
based duplicate.
Active DB duplicate copies the live TARGET DB over the network to the AUXILLARY
destination and then create the duplicate database. In an active duplication process,
target database online image copies and archived redo log files were copied
through the auxiliary instance service name. So there is no need of target db backup.