In our Application, Process models are chained. User can step back to any node a

In the Process Modeler, open the node that save data to DB, you have to uncheck "Allow users to step back to this node from the next chained activity." in Other tab.
If you only want data to be written once, you can't let user go back to this node.

MNI instance number is the number of instances that will be executed each time the node is activated. So this won't help you.

If you still see the need to let user go back to previous nodes (before the save to DB), you'll have to do the flow navigation based on additional buttons on the UI screen, instead of relying on the Step Back feature. You also need to think about what do you want to do with the data already written, if the user made some changes. Most likely, you'll have to do the update, instead of inserting new row.

In the Process Modeler, open the node that save data to DB, you have to uncheck "Allow users to step back to this node from the next chained activity." in Other tab.
If you only want data to be written once, you can't let user go back to this node.

MNI instance number is the number of instances that will be executed each time the node is activated. So this won't help you.

If you still see the need to let user go back to previous nodes (before the save to DB), you'll have to do the flow navigation based on additional buttons on the UI screen, instead of relying on the Step Back feature. You also need to think about what do you want to do with the data already written, if the user made some changes. Most likely, you'll have to do the update, instead of inserting new row.