Describing Tenant Replication

Objective

After completing this lesson, you will be able to examine the setup of tenant replication

Copying and Moving Tenant Databases Between Systems

Using SAP HANA system replication mechanisms, SAP HANA tenant databases can be copied and moved securely and conveniently from one SAP HANA system to another with near-zero downtime. This allows you to respond flexibly to changing resource requirements and to manage your system landscape efficiently.

Copying and moving a tenant database are essentially the same processes. First, the tenant database is copied through the replication of all of its data to a newly created tenant database in a target system. Once all data has been successfully transferred, the new tenant database is started as a separate, independent database. If the aim is to move the tenant database to the new system, the original tenant database is deleted and the new tenant database takes over.

Tenant replication always starts with replicating the data. When the databases are in sync, the closure depends on the selected replication option. With the copy option, the replication stops and the source and target are available. With the move option, the replication stops, the target tenant is made available, and the source tenant is deleted.

Therefore, the only difference between copying and moving a tenant database is what happens to the original tenant database after all data has been transferred to the new tenant database in the target system.

In both cases, the new tenant database starts running as a fully separate, independent database.

Several tenant databases can be copied or moved to a system at the same time. It is also possible to copy or move a tenant database to a system with a different isolation level than the source system.

You can also use this mechanism to create a copy of a tenant database on the same host or to copy/move a tenant database to another host that is part of the same system.

Prerequisites and Implementation Considerations

  • A new tenant database will be created in the target system. Therefore, the target tenant database must not already exist in the target system.

  • The target system must have a software version equal to, or higher than the source system.

  • During the copy and move process, data must be replicated using a secure (SSL/TLS) network connection by default.

  • In a running system replication, it is possible to copy or move tenant databases into a primary system, or from a primary system into another target system that is different than the secondary system.

  • There can be no changes to the topology of the original tenant database while the move or copy is in progress.

  • If the source system is configured for host auto-failover, the copy or process fails in the event of failover to a standby host.

  • The administrator has the system privilege DATABASE ADMIN.

  • Tenant replication is configured.

  • A complete system backup for the source tenant database has been created.

Create a Tenant Database Using the SAP HANA Replication Mechanism

The figure, Create Tenant Using Replication, describes how to create a new tenant, based on an existing tenant using the SAP HANA replication mechanism on a target system performed with the SAP HANA Cockpit tool.

SAP HANA Cockpit: The steps to create a new tenant using tenant replication are shown.

To create a new tenant database, proceed as follows:

  1. To create a new tenant based on an existing tenant, on the Database Management screen of your SAP HANA target systems SYSTEMDB, choose Create Tenant → Create Tenant Using Replication.

  2. Follow the guided steps. To create a copy of an existing tenant database, select Copy using replication. To remove the original tenant after the copy has been created, select Move using replication. Choose the source system and tenant databases and enter a name for the new tenant.

  3. Perform the following steps:
    • Optional: Specify the number of the internal communication port of the listed services.
    • For high isolation systems only: Enter a dedicated OS user and group for the source.
    • If configuration changes are required for the replication, warnings appear to indicate the required changes. Select Approve to proceed.
    • If prompted, enter the SAP Control credentials required for the restart of the system.
    • If a trust relationship has not yet been established between the source system and the target system, select an existing public key certificate or upload a certificate.
    • Review the summary, then choose Copy Tenant Database or Move Tenant Database, to start replicating the tenant database.

  4. The new tenant database appears in the list of databases of your target systems SYSTEMDB.

Note

For detailed information about creating tenant databases using replication, please check the SAP HANA Administration Guide and the SAP HANA Administration with SAP HANA Cockpit document.

Copy a Tenant Database Using the SAP HANA Replication Mechanism

The figures, Copy Tenant Using Replication (1, 2, and 3), describe how to copy a tenant database to another system using the SAP HANA replication mechanism and the SAP HANA Cockpit tool.

SAP HANA Cockpit: The steps to create a new tenant using copy tenant replication are shown.
The wizard gives an overview on the security and configuration changes that need to be performed before tenant replication can be activated.
During the activation and copying of the tenant the wizard show the progress.

To copy a tenant database, proceed as follows:

  1. On the Database Management screen of your SAP HANA source systems SYSTEMDB, mark your source tenant.

  2. Choose Tenant Actions → Replicate Tenant Using Replication.

  3. Choose Copy using replication. The Source System Database and the Source Tenant will be provided automatically.

  4. Choose Target System Database and enter a name for the Target Tenant.

    • Optional: Under Advanced Settings, specify the port number for each service. If you do not enter a port, it is assigned automatically based on port number availability. In multihost systems enter the host and port of a service.
    • For high isolation systems only: Enter a dedicated OS user and group for the source.

  5. If configuration changes are required for the replication, warnings appear to indicate the required changes. Select Approve to proceed. If prompted, enter the SAP Control credentials required for the restart of the system.

  6. If a trust relationship has not yet been established between the source system and the target system, select an existing public key certificate or upload a certificate.

  7. Review the summary, then choose Copy Tenant Database, to start replicating the tenant database.

  8. Observe the following:
    1. The Progress page shows the running configuration process, the system restarts, and the certification installation.
    2. After finishing, the progress bar indicates the status of the tenant replication.

  9. The copied tenant database appears in the Database Management screen of the target systems SYSTEMDB.

Move a Tenant Database Using the SAP HANA Replication Mechanism

The figures, Move Tenant Using Replication (1 and 2), describe how to move a tenant database to another system using the SAP HANA replication mechanism and the SAP HANA Cockpit tool.

SAP HANA Cockpit: The steps to create a new tenant using move tenant replication are shown.
During the activation and moving of the tenant the wizard show the progress.

As mentioned before, copying and moving a tenant database are essentially the same process.

There are the following differences:

  • In step 3, choose Move using replication. This will remove the original tenant after the copy has been created.
  • In step 5, the button is named Move Tenant Database.

Note

The process of copying and moving tenant databases is described in detail in the SAP HANA Administration Guide and the SAP HANA Administration with SAP HANA Cockpit document.

Copy and Move Process

The process of copying or moving a tenant database is driven entirely by the target system.

  1. To prepare the copy and move process, the system administrator performs the following tasks:

    • Verifies that TLS/SSL is enabled on internal communication channels.

    • Opens communication from the target system to the source system by enabling source system services to listen on all network interfaces.

    • Creates credentials for authenticated access to the source system.

    • Configures a secure connection from the target system to source system.

    • Backs up the source tenant database.

  2. The system administrator triggers the creation of the tenant database as a replica of the source tenant database by executing the SQL statement CREATE DATABASE AS REPLICA.

  3. During the copy process, the system database of the target system performs the following tasks:

    • Establishes a secure connection to the system database using the stored credentials created earlier.

    • Creates a new tenant database with the same topology as the tenant database in the source system.

    • Initiates replication of data between the services in the source tenant database and the corresponding services in the target database.

    • Commits the copy by executing the SQL statement ALTER DATABASE FINALIZE REPLICA when the replication status is ACTIVE.

  4. To finalize the copy and move process, the following steps are performed:

    • The system database of the target system starts the target tenant database and performs clean-up operations.

    • The system administrator performs manual post-copy or post-move steps.

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