How to Define Role to different Server Nodes in Multi Node HANA System
The standard SAP recommended Node role would be as follows:
In the above screen shot we have three nodes in which the first node has been set as Master node for Index and Name server.
a). Name Server contains the topology of the HANA landscape and its detail structure.
b). Index Server Holds all Data and Executes all the operations.
This is the reason Index Server and Name Server are the most critical services in HANA.
If Host is defined as STANDBY in “/hana/shared/<SID>/global/hdb/custom/config/nameserver.ini” file then it appears as IGNORE in HANA Studio. Also the corresponding Index Server (Configured as well as Actual) is appearing as STANDBY.
Please see the screen shot below for more information on how role of different Servers are mapped according to Role defined for HOST and Name Server:
Hence HOST which is defined as STANDBY the corresponding Configured Role of Name Server would be SLAVE and the corresponding Index Server Role would be STANDBY.
Name Server and Index Server Role:
The Role of Index Server depends on Role of Name server whose detail is given below:
From the above it is clear that the Name Server Node which is configured as “Master1/Master2/Master3…” can be either MASTER or SLAVE when we see it’s Actual Server Node Role. Configured Name Server Role as SLAVE depends on HOST defined as STANDBY. For more information, see above screen shot above about host role.
For Index Server is it is configured as WORKER then in Actual Role it is either MASTER or SLAVE depending on the corresponding Actual Name Server Role. Hence Actual Role of Index Server configured as WORKER and is on MASTER Name Server is having Actual Role of MASTER and other work as SLAVE.
If Index Server Falls on STANDBY host it’s Configured as well as Actual Role appear as STANDBY. This can be verified through the following screen shot:
In the case of Name Server configured as MASTER1/MASTER2/MASTER3.. is not available then the STANDBY Host is getting utilize and Name Server and Index Server gets activated on the STANDBY host with Actual Role shown as SLAVE for both in the HANA Studio and the Status of the HOST gets changed from IGNORE to INFO.
Also the HOST which is not available is showing as INFO in the Status column of the HANA Studio. Please see the detail below for more information on how the role gets changed after one server is not available.
There are two option to make the Role change:
1). By Modifying the file “/hana/shared/<SID>/global/hdb/custom/config/nameserver.ini” and taking restart of the HANA server.
2). Through SAP HANA Studio as follows:
Once done then the HANA application needs restart through ‘hdb’ command at OS level by <sid>adm user.