Synchronization in WAS - WebSphere Application Server Interview Questions - Part -11

Q)  What are the different types of synchronizations available ? Explain which type if better and any disadvantages ?

 
Def Of Synchronization : Whenever there is change in Master Repository. Node Agent handles all the Synchronization process.

 There are two types of Synchronization in the Websphere

1)  Automated Synchronization 

a. Start-up time synchronization which will happen whenever the websphere components start.
b. Interval based synchronization which can be configured in the nodes configuration. default time : 60

2)  Manual Synchronization

a. Manual synchronization can be achieved with the save and synchronize option provided in console.

----> Normal (partial) synchronization (only synchronization files dmgr thinks have changed)

-----> Full synchronization (synchronize all files in the repositories)

NODE AGENT :

Q)  What is the effect on end-user in case the dmgr goes down or node agent stops?

A)  ----> There is no effect on the end user if the DMGR goes down or the Nodeagent goes down, because nodeagent is mediator between dmgr and app Server

-----> The app server will continue running if everything was running before and we have stopped the dmgr and nodeagent. I believe the app server will continue running(need to test things in my dev environment). 

-----> In case if we say that everything is stopped and we try to start only the application server, keeping the dmgr and nodeagent down

-----> Because the nodeagent should be running before starting the application server.

-----> If the NodeAgents are down, you would not be able to sync the changes you made on the application server to the Deployment Manager. Nodeagent is just the connection between DMGR and the AppServer.

----> DMGR is the Master Repository.

----> Node Agent Plays important role between Cell members, Its possible that 2 diff applications are communicating and its possible that an application has some dependency on another application running on another application server. So nodeagent helps 2 diff applications servers communicate with each other. Also whenever an application server starts, the node agent should be running as application server registers himself with nodeagent, if the nodeagent is down, the application server will fail to start. So, Its always recommended that the nodeagent should be running.

Q) How many ways we can Synchronize node ?

A) There are 2 ways of node Synchronization.

     1) From Command Prompt : Stop the node issue "syncNode"

         <Node_Host>/bin> SyncNode<DMGR_Host> <DMGR_PORT> [options]

         -username,-password,-restart,-connType,-Quit,-stopServer

    2) From AdminConsole : SystemAdministration-----> Nodes -----> Synchronise 

BACKGROUND PROCESS OF SYNCHRONIZATION : 

      

Step 1: Node Agent initiates Synchronization operation.

Step2: Cell reads Master Configuration repository and compares to node copy information.

Step3 : Cell return update information and files.

Step4: Node writes updates to local configure files (All changes at once)

PROCEDURE :

NodeAgent  ------> fileSynchronization

Startup Synchronization ---> with start of node agent

----> If any manual change is done use full Synchronize


FILE SYNCHRONIZATION :

1) Configuration updates mode at the DMGR are synchronized with the node via the Node Agent

2) DMGR and Node Agent use the File Transfer applications to transfer the file over HTTP

3) Updates are pulled by the Node Agent during File Synchronization.

4) Only One way Synchronization.

-----> Changes saved at the DMGR level are propogate down.

5) Uses HTTPS if security is turned on.

-----> With the installation of  WAS7 we get simple default in WAS_root (Simple Library) JYTHON Scripts.



----> To execute the commands we have two modes.

1) Command mode (Interactive,Single Command)

2) Batch mode (more command in a single file)