Using the Central Console (GUI) - recommended
From Dbvisit Standby you will notice a couple of new options in the main screens Reporting Replicas [ 1 ] and Test/Dev Snapshots [ 2].
Before you navigate to the new Menu options, it is important to make sure you already have a Dbvisit Standby Configuration (DDC) configured for a Primary => Standby pair, a Standby Database is configured (could be a Cascading standby database, but doesn't have to be).
Now you will notice the following as highlighted in the image above:
- Reporting Replicas
- This is the option you will use to create a logical grouping of Read-Only standby databases that will give you the effect of an updated read-only environment that can be used for reporting purpose or data extraction
- Test/Dev snapshots
- The second option is where you can create Single Snapshots which can be read-only or read/write.
Before we get into the details of each of these options, it is important to know that each of these configurations are linked to a specific DDC (Dbvisit Standby Configuration) - you must also have already applied the Licence Key with the new option enabled before you will be able to create snapshots. All pre-requisites must also be met - in short, the Standby Database is on a Logical Volume and Linux is used.
Clicking either the New Snapshot Group or New Single Snapshot button will bring up a DDC selection dialogue:
After choosing the DDC, a number of pre-checks are performed:
- Is the environment suitable for Snapshot creation (looks for Linux + LV)
- Is the chosen DDC licensed to use Dbvisit Snapshots
- (For Snapshot Groups) Is there already an existing Snapshot Group configuration on the chosen DDC. You cannot have more than 1 Snapshot Group on a single DDC.
If any of these fail, an appropriate error message is displayed. Otherwise, a form is shown with some basic input required from the user:
- (Not user editable) The Logic Volume that will be used for the Snapshot.
- (Not user editable) The Mount Point that will be used for the Snapshot. This is always the same as the mount point of the standby DB, for simplicity's sake.
- (Not user editable) The Volume Group that the Snapshot will belong to. This is also the same as the standby DB.
- The Oracle Service Name is chosen by the user. This is the name that will execute the dbvsnap utility.
- If you need your snapshot groups to be in read-only or read-write mode (The database is activated)
- The desired number of Snapshots to create/maintain. Allowed values are currently 1 - 4. This is the number of Snapshots that will be kept and switched between every Creation Interval setting (below).
- Snapshot Creation Interval - in minutes, how frequently to create new Snapshots (and potentially delete old ones). We recommend this is no less than 10 minutes.
- A prefix that will be applied to the names of all created Snapshots. This is provided so that users can easily tell which Snapshots on their system were created by this utility. This is limited to 5 characters, alphanumeric only.
- An optional field you can use to specify custom parameters for the mount operation. For advanced users.
- The maximum allowed size for a Snapshot to reach. A default value is provided, but it is up to the user to ensure this is set appropriately to their intended use for the Snapshot. Make sure this is not too small - you wouldn't want your Snapshots to run out of space!
- Advanced option to provide custom database parameter. The default value is provided for sga_target, should only be changed by expert users. The other database parameters can be added/modified. Below figure shows how.
When using XFS filesystem you have to specify to "Mount Option" field value: "-o nouuid" (without quotes) otherwise snapshot creation would fail
After the parameters are set, click the Create button to create a new Snapshot Group.
At this stage you can see the Group is created, but the daemon that manages the Snapshots is not yet running, and no Snapshots yet exist. Click the green Play button to initiate the Snapshot Group with accordance to the settings you provided.
The Snapshot Group is now running, and new Snapshots are being created every Creation Interval. Initially, the numbers may show 0 Snapshots (0 Mounted), but you will see them change very quickly as the first Snapshot is created & mounted, and thereafter as the process runs. If an active (i.e. running) Snapshot Group exists, this page is continually updated (every few seconds) to ensure the shown information is always correct.
To get more detailed information about the Snapshot Group, click the View Details button to bring up the diagram view.
The space allocated 665MB/2147MB. The 665M indicated will be the initial size of the snapshot which is nothing but the space occupied by redolog groups and the controlfile which gets created for the activated read-write and read-only snapshots which should be taken into consideration when creating snapshots both single and group.
Here you can see the origin and settings of the Snapshot and Volume Groups in the information boxes on the left, and detailed information for each Snapshot in the Group on the right. For each Snapshot, the following information is available:
- Snapshot name
- Created timestamp
- SCN number at the time of the creation
- Leader indicator, i.e. which Snapshot will all new connections to the DB connect to
- The state of the database inside the Snapshot
- Snapshot total allocated size, plus how much is being used right now [1 ]. The space allocated 665MB/2147MB. The 665M indicated will be the initial size of the snapshot which is nothing but the space occupied by redolog groups and the controlfile which gets created for the activated read-write and read-only snapshots which should be taken into consideration when creating snapshots.
- The number of active connections, if any
- Information on whether or not the Snapshot is mounted
This detailed view provides read-only information only, no user actions are possible. If the Snapshot Group in question is active, i.e. the daemon is running, this screen will continually update to display near to real-time information.
You may control the Snapshot Group using the buttons on the right-hand side of the table, as follows:
- (1) Yellow Pause - Pause Snapshot generation. No new Snapshots will be created, however, all existing Snapshots will remain mounted.
- (2) Yellow Stop - Stop Snapshot generation, shut down database instances but does not umount the snapshots.
- (3) Red Remove - Stop Snapshot generation, and unmount and REMOVE all Snapshots.
Once the red remove action is used, a 4th option appears in place of the option (3) above:
- Red Delete - Remove the Snapshot Group configuration. This will remove the Snapshot Group definition/configuration from the system, returning it to the state it was in prior to any Snapshot Group actions.
The settings for a Test/Dev Snapshot are largely the same as those used for Reporting Replicas (discussed above).
Creating a Snapshot does take some time (30 - 180+ seconds). While the Single Snapshot is being created, a working indicator popup is displayed to the user. Once the Snapshot is ready, it is visible in the appropriate table (note the TEST Snapshot below):
Just as with Snapshot Groups, it is possible to see detailed information for the Snapshot by clicking on View Details. Single Snapshots have only one available user action, which is to delete the Snapshot using the Red Delete button.
Using a Test/Dev Snapshot for DR Testing
One of the use-cases for Single Snapshots is using them for DR testing, instead of backing up the standby DB, performing the tests, and then re-instantiating. This use-case is built-in to the Snapshots Utility.
To begin, go to the Disaster Recovery Actions page as normal, select your DDC (note the new selector component) and "Perform DR Test" → "Run DR Test".
On environments which are Snapshot-capable (as defined by the requirements at the beginning of these docs), AND licensed to use the Snapshot utility, you should see a new option appear, as above.
This option essentially advises the user of their ability to do DR testing via Snapshot creation, and offers a link to proceed directly to the Snapshots page. The user can still select not to do this, and to instead proceed with a normal, backup→reinstantiate DR test by using the available switch toggle.
Click the link to go to the Standby Snapshots page.
If accessing this page from the Disaster Recovery Actions link, the user will be presented with a helper popup describing the process of using a Single Snapshot for DR test purposes.