Description:-
- Oracle Database 11g introduced the Snapshot Standby feature in Data Guard
- A snapshot standby database is a fully updateable standby database created by converting a physical standby database into a snapshot standby database.
- A snapshot standby database receives and archives, but does not apply, redo data from a primary database.
What is a snapshot standby database?
A snapshot standby database is a fully updateable standby database created by converting a physical standby database into a snapshot standby database. A snapshot standby database receives and archives, but does not apply, redo data from a primary database.
Is there a redo flow to snapshot standby database?
There is redo flow to Snapshot Standby Database, but there is no redo apply. As soon as the Physical Standby Database is converted to Snapshot Standby Database, an implicit restore point is created and Flashback logs are activated. Besides being a nice feature to be updated, Snapshot Standby Database also has dangerous points.
What happens to the snapshot database after the testing?
Once the testing is over we can again convert the snapshot database to physical standby. Once it is converted physical standby database, whatever changes were done to the snapshot standby will be reverted.
What is a snapshot and how does it work?
As mentioned, a snapshot preserves the disk and/or VM state at a specific point in time by creating a series of delta disks for each attached virtual disk or virtual RDM. Optionally, the memory and power state are preserved by creating a memory file.
How do I start a standby database snapshot?
Let start the Snapshot Standby database Demo:-Dataguard Configuration:-Step:1 Check both primary and standby role.Primary:-Step 2:- Check the archived sequence in standby,Step 3:- Check the flashback status and db_recovery_file_set location,alter database recover managed standby database cancel;More items...
How does Oracle Data Guard work?
Oracle Data Guard ensures high availability, data protection, and disaster recovery for enterprise data. Data Guard provides a comprehensive set of services that create, maintain, manage, and monitor one or more standby databases to enable production Oracle databases to survive disasters and data corruptions.
How do you convert physical standby to logical standby?
Create a Physical Standby Database.Stop Redo Apply on the Physical Standby Database.Prepare the Primary Database to Support a Logical Standby Database.Transition to a Logical Standby Database.Open the Logical Standby Database.Verify the Logical Standby Database Is Performing Properly.
How do I create a standby database read write?
SolutionStep 1 – In Standby database.Step 2 – In Primary Database.Step 3 – In Standby database.Step 4 – In Standby database.Step 5 – In standby database.Step 6 – In standby database. A ) Put the standby database in managed recovery mode. ... Step 7 – In Primary database. ... Step 8 – In Standby database.More items...•
What is the difference between switchover and failover?
Answer: In general, a failover is a production emergency, where the primary database has failed and you need to failover to the standby database. Conversely, a switchover is a planned switch from a standby back to the primary database, a non-emergency operation.
What is the difference between Data Guard and Active Data Guard?
The main difference between Oracle Data Guard and Active Data Guard is that Oracle Data Guard is an extension to the Oracle RDBMS that provides data availability and protection while Active Data Guard is an extension of Oracle Data Guard that improves the production database performance for critical transactions.
What is the difference between physical standby and logical standby?
Definition. The logical standby database is a database that does not have the schema structure exactly similar to the source database. In contrast, a physical standby database is a database that replicates the exact contents of its primary database across the Oracle Net Network layer.
How do I check logical standby?
If you would like to know the brief status of the logical standby sql apply status, we can query "v$logstdby_state" this view provides consolidated information from views v$logstdby and v$logstdby_stats.
What is logical standby database in Oracle?
Logical standby databases A logical standby database is kept in sync with the primary by transforming redo data received from the primary into logical SQL statements and then executing those SQL statements against the standby database.
How do I know if my standby database is primary?
You need to create a script for sqlplus. In the script, you first get the tns_alias standby bd from the log_archive_dest parameter. Then connect to standby bd as sysdba. Uodate 1 You can run the query on the main server and see the active sessions from the standby server.
How do you find the gap between primary and standby databases?
Step by Step Process to Resolve gap on the Standby database.Check the name and status of database.Check for GAP on standby.Check redo received on standby.Check redo applied on standby.Identify missing archive log files.Copy archive log files.Register archive log files with standby.More items...•
How do you stop MRP in standby database?
To stop the MRP, issue the following sql statement. ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL; Earlier on RAC environments, MRP process can be run only from one instance on standby site.
What are the advantages in using Oracle Data Guard?
Advantages. Data Guard provides high availability for a database system. It can also reduce the human intervention required to switch between databases at disaster-recovery ("failover") or upgrade/maintenance ("switchover") time. Through the use of standby redo log files, Data Guard can minimize data loss.
What is Data Guard broker and how it is useful?
Oracle Data Guard Broker is a centralized framework that automates the configuration, management, and monitoring of an Oracle Data Guard configuration. Oracle Data Guard Broker further enhances Oracle RAC by providing apply instance failover for Oracle RAC standby databases.
What is difference between Data Guard and RAC in Oracle?
rac is a cluster of machines (nodes) whereby the oracle instance is being switched around if the node which houses the instance has some problems? dataguard is a configuration of 2 machines. one is the production and the other is the standby, exact replica of the production.
What is Data Guard in OCI?
Oracle Data Guard maintains the standby database by transmitting and applying redo data from the primary database. If the primary database becomes unavailable, then you can use Oracle Data Guard to switch or fail over the standby database to the primary role.
What is a snapshot standby?
A snapshot standby database is a fully updatable standby database that is created by converting a physical standby database to a snapshot standby database. A snapshot standby database receives and archives—but does not apply—redo data from a primary database. Redo data received from the primary database is applied when a snapshot standby database ...
What happens when a snapshot database fails?
If the snapshot standby database lags far behind the primary database , it may take a long time to apply the redo that has been received and convert it to the primary database.
Does snapshot standby accept redo logs?
The snapshot standby database accepts redo log files but does not apply them. If there is a corrupted redo log file at the snapshot standby database, it is not discovered until the database is converted back to a physical standby database and the managed recovery process (MRP) is started. If the primary database is unavailable at that time, there is no way to retrieve that log. Also, the loss or corruption of a flashback log file might prevent conversion back to a physical standby database.
What happens to a standby database while it is in snapshot mode?
Let’s say something happens to Primary Database while Standby Database is in Snapshot mode. In this case, it will be rewound with Flashback logs first. Since it will run the archives later, it means an interruption for as much as this time.
What happens when a physical standby database is converted to a snapshot standby database?
As soon as the Physical Standby Database is converted to Snapshot Standby Database, an implicit restore point is created and Flashback logs are activated.
What is Oracle Snapshot Standby Database?
Snapshot Standby Database is an updatable database created from Physical Standby Database.
Why is there only one standby database?
The reason is that when there is only one Standby Database, it must be sync with Primary as much as possible so that it can be Primary quickly if a Failover occurs .
What does transportdisconnectedThreshold mean?
TransportDisconnectedThreshold: Indicates that the last communication with the Primary has exceeded the specified threshold. After this exceed, Primary cannot send redos to this location. Default is 30 seconds.
What Is Snapshot?
A storage snapshot is a set of reference markers for data at a specific point in time. A snapshot is like a detailed catalog, providing users with an accessible copy of the data they can roll back to. Now, you can continue to read this post from MiniTool to get more information about the snapshot.
How Does Snapshot Work?
Storage snapshots are usually based on the use of differencing disk. A differencing disk is a special type of virtual hard disk that is linked to a parent virtual hard disk.
Type of Snapshot
The implementation of storage snapshot technology varies by vendor. There are different types.
Snapshot vs Backup
Snapshot backups are primarily used to restore systems, virtual machines, and disks or drives to a running state and serve as a recovery point for the system when a snapshot was taken. It is not equivalent to a backup copy, it does not store data itself, but only defines where and how data is stored and organized.
What does Snapshot collect?
What information does Snapshot collect? Snapshot collects information about how you drive, how much you drive, and when you drive. If you're using the Snapshot Mobile app, details about your handheld phone use behind the wheel will also be collected.
What is Snapshot driving?
With Snapshot, we measure a variety of factors related to your driving, including things such as the time of day you drive, sudden changes in speed (hard brakes and rapid accelerations), the amount you drive, and, for customers using the mobile app in some states, how you're using your mobile phone while driving.
What is GPS on a phone?
The mobile app uses GPS to calculate your speed over time, mileage, and driving behaviors such as hard braking. Location data is used to provide trip information on the phone. It may also be used for underwriting purposes but is not used in determining your personalized rate.
What is Snapshot insurance?
Typically, car insurance rates are based on a variety of factors related to your driving history or the histories of drivers who are similar to you. Snapshot prices your insurance differently and personalizes your insurance rate based on your actual driving (called usage-based car insurance insurance ). The better you drive, the more you can save.
How to contact Snapshot Mobile?
If this is the case and you would like to try Snapshot, you can call us at 1-877-329-7283 or log in to participate in the Snapshot program with the plug-in device.
How many miles does Snapshot cover?
The Snapshot Mobile app is a good fit if all drivers on the policy have an Android™ phone or iPhone ® smartphone, and if each of the drivers on the policy puts at least 4,000 miles a year (about 10 miles a day) on their vehicle.
How to see how you're doing on Snapshot?
Look for regular email updates showing your progress during the Snapshot program. You can also log in to your policy at any time to see how you're doing . When you have completed monitoring, you'll get an email with your Snapshot results and information on sending back the plug-in device or deleting the mobile app.
What does snapshot do in VM?
Snapshot the virtual machine’s memory: Enabled by default, this option flushes the memory content of a VM to disk as part of the snapshot. This allows a VM to revert back to the exact state it was running in when the snapshot was taken. If this option is deselected, and quiescing is not selected either, the snapshot will create files which are crash-consistent, meaning you’ll need to power up the VM manually after having it restored from snapshot. A memory snapshot will significantly take longer to complete. Additionally, a VM is “frozen” to ensure state integrity.
How does snapshot affect virtual machine performance?
Snapshots can negatively affect the performance of a virtual machine. Performance degradation is based on how long the snapshot or snapshot tree is in place, the depth of the tree, and how much the virtual machine and its guest operating system have changed from the time you took the snapshot.
Why do you need snapshots in VMware?
The VMware snapshot feature is particularly useful in those scenarios where you want to quickly recover from a failure or simply revert back to a desired state. Restoring a VM to a functional state following a botched update or patch is one common use-case. Similarly, you can use snapshots to reset a VM back to a baseline state once a user is done using it, perhaps as part of a training lab maintenance regimen.
How to revert back to snapshot?
To revert back to a snapshot, you either select the Revert to Latest Snapshot option. If a VM has multiple snapshots, just highlight the snapshot you want to revert to from the snapshot hierarchy displayed in Snapshot Manager and hit the Revert To icon as shown in Fig. 6.
Is snapshots of VMs configured for bus sharing VMware supported?
Snapshots of VMs configured for bus sharing is not a VMware supported option.
Do you need to be powered off before taking snapshots?
VMs with independent disks must be powered off before you take a snapshot. Snapshots of powered-on or suspended VMs with independent disks are not supported. Snapshots are not supported with PCI vSphere Direct Path I/O devices. Snapshots of VMs configured for bus sharing is not a VMware supported option.
Can snapshots affect VM disks?
There might be instances where you do not want VM’s disks to be affected by snapshots. To achieve this, change a VM’s hard disk Disk Mode to Independent – Persistent or Independent – Nonpersistent from the VM’s settings. The two options differ slightly as per VMware’s explanation:
