Is there any OOTB feature available in appian to update the pv variables of the inflight instances apart from IFM (In-flight Modification) plugin? please suggest.

That is the only way. What are you looking for?

I basically want to update a pv variable for a list of inflight instances. 

Did you check this?

Changing process variables

It's possible to change the value of process variables in a process instance. The approach differs based on the type of the variable.

To change process variables of system data types:

1. From the toolbar, select the Process Model Properties icon to view the process variables.
2. Select a process variable to update it.
3. For a process variable of type multiple, insert the value with a comma separator. For example, to add an array of two values to a process variable of type Text, enter text string 1, text string 2.

To change process variables of custom data types, you need to add a script task to your process model that stores the new value into the variable:

1. Edit the process.
2. Drag and drop a script task onto the canvas.
3. Add a node input, and choose the custom data type as its type.
4. Set the new values.
5. Save the node input into the process variable that you want to update.
6. Apply your changes to the process instance.
7. Switch to Monitor mode.
8. Close the tab open in Edit mode.
9. Right-click on the new script task and select Start.

To change an encrypted text value, you can use a technique similar to modifying values of custom data types:

1. Edit the process.
2. Drag and drop a User Input task onto the canvas.
3. Add a node input of type Encrypted Text.
4. Configure an interface that displays the encrypted text value and saves the updated value back into the node input.
5. Save the node input into the process variable that you want to update.
6. Apply your changes to the process instance.
7. Switch to Monitor mode.
8. Close the tab open in Edit mode.
9. Right-click on the new User Input task and select Start

docs.appian.com/.../Monitoring_and_Editing_Processes.html

Did you check this?

Changing process variables

It's possible to change the value of process variables in a process instance. The approach differs based on the type of the variable.

To change process variables of system data types:

1. From the toolbar, select the Process Model Properties icon to view the process variables.
2. Select a process variable to update it.
3. For a process variable of type multiple, insert the value with a comma separator. For example, to add an array of two values to a process variable of type Text, enter text string 1, text string 2.

To change process variables of custom data types, you need to add a script task to your process model that stores the new value into the variable:

1. Edit the process.
2. Drag and drop a script task onto the canvas.
3. Add a node input, and choose the custom data type as its type.
4. Set the new values.
5. Save the node input into the process variable that you want to update.
6. Apply your changes to the process instance.
7. Switch to Monitor mode.
8. Close the tab open in Edit mode.
9. Right-click on the new script task and select Start.

To change an encrypted text value, you can use a technique similar to modifying values of custom data types:

1. Edit the process.
2. Drag and drop a User Input task onto the canvas.
3. Add a node input of type Encrypted Text.
4. Configure an interface that displays the encrypted text value and saves the updated value back into the node input.
5. Save the node input into the process variable that you want to update.
6. Apply your changes to the process instance.
7. Switch to Monitor mode.
8. Close the tab open in Edit mode.
9. Right-click on the new User Input task and select Start

docs.appian.com/.../Monitoring_and_Editing_Processes.html

Hi David,

Thanks for your suggestion, but this is not what iam looking for. My requirement is not to update the pv for just 1 instance, it is for multiple instances programatically.  I tried using IFM smart service and it is working. I want to check if there is any other better option than IFM. 

Is that for a rare support case or do you plan to make this part of the overall solution design?

No not for support case, it is for part of the solution. 

That is not something I recommend. What problem do you want to solve?

DO yu want to do this only once? or is something that you will have to to do periodically?

If it's the second case, I would suggest to change the way your process are implemented..... in order to support this behavior...

Yes David it is the second case. That is what even i am thinking about, before that just want to explore other possible options.