SAP PM Change Maintenance Strategy in General Task List

I want to change Maintenance Strategy in General Task List within Tasklist Group. E.g. Tasklist "T3" - Counter 3 with Maintenance Strategy

"A" to "B". Tasklist "T3" has been used for several times in scheduling.

I try to use IA06, Goto T3 Header - and found Maintenance Strategy at Header was Gray. I don't find this documentation in SAP Help.
Is it possible change Maintenance Strategy in Tasklist after created?

To change the strategy of a task list which has already been used, we should check the following conditions.

1. The task list should be removed from all maintenance items.
2. Then maintenance package ticks in the task list has to be removed.
3. Then system allows you to change the strategy.
4. Then assign the new maintenance packages (Tick marks).
5. Now assign the task list back to maintenance items.

Trust this shall be useful to you.

Once the Task list has been created with one maintenance strategy it is not possible to change it to another strategy type. You can delete the strategy provided you have not used it in maintenance items. But in your case it is not possible.

You cannot change a strategy as you know, Copy the task list you want to change, then create the new strategy on your new task list.
Then create a new maintenance item and allocation of the task list with the correct maintenance strategy.
Then create a new maintenance plan and link maintenance item.

Maintenance strategies if I am not using any calender

While creation of maintenance strategies if I am not using any calender, then system will use which calender days shedule plans?

Is it 365 days working?

This depends on the Scheduling indicator you choose for the Plan!

If you select "Time", then, it will be based on 365 days an year.
If you select "Factory Calender", you need to specify the FC.

Maintenance strategy.Transaction code-ip11

I entered following parameters in the strategy.

Scheduling indicator -Time
Strategy unit -MON
Shift factor for late confirmtion -60 %
Tolerence for late confirmation -100%
Factory calender w8.

All above parameters are getting transpered to Strategy Maintenance Plan (Tran.code ip42) except factory calender.

Can any body tell me what will be the cause of problem.

Scheduling indicator = Time factory calendar does not matter
If you want factory calendar to work choose
scheduling indicator = time-factory calendar.