In this paper, I will describe the Replication structure and installation stages of the HANA Database, which is the HA (High Availability) feature. Before proceeding with the installation, it is necessary to mention the replication and operation modes.
3 different replication modes, Synchronous, Synchronous in Memory, Asynchronous
There are 2 different operation modes including delta_shipping and logreplay.
- Synchronous: This is the process of synchronization only from the disk.
- Synchronous in Memory: This is the process of synchronization via memory.
- Asynchronous: The process of synchronization made over disk and usually established for DR site.
- delta_datashipping: At the end of each transaction, the difference data is discarded.
- logreplay: At the end of each transaction the difference data is discarded with logs.
First of all, it is entered into the configure system replication field from the configuration and monitoring tab.
We select Enable system replication and open the system replication feature in the corresponding system.
The primary system of the replication structure is named.
Then we need to do the same in our Secondary host.
However, the secondary host must be closed. We will open the system with replication.
In the secondary system, the same is entered in the Configration System Replication field. Here we select the seconday system button register this time.
Here, the name, replication and operation modes to be assigned to the secondary system are determined.
Then the source host is registered.
If Initiate Full Data Shipping is selected at the bottom, first the full data is then discarded.
When Start secondary system after registration is selected, the system starts the secondary server automatically and the synchronization process starts.
One of the important points here is to select the correct replication mode and the correct operation mode. In the same location, even systems in the same DC must be connected to each other as Synchronous in Memory, and systems at different locations as Async.
To disrupt the replication structure, the secondary system is switched off.
Then select the Unregister Secondary System button from the relevant field and continue.
From the primary system, the same field is entered and Disable System Replication is selected and resumed.
Ignore Secondary System is selected and the process is finished.
We can do this from the Linux terminal. A simple replication structure can be established with the following linux commands.
A: Primary Site
B: Secondary Site
[A] HDB start: DB opens.
[A] hdbnsutil -sr_enable <SID>: Replication is enabled.
[B] HDB stop: DB is closed.
[B] hdbnsutil -sr_register <SID>: The source system is specified and registered.
[B] HDB start: DB is turned on again and the synchronization process starts.
Suleyman Kas – Database Administrator