Hi Dharmakasi,
Thanks for your inputs.
In standard if we change the item system status to completed then header status will be set to the same.
In our case the method which we are using in the action definition, we were trying to change both user status and system status, in the item level only user status was getting set but system status was not getting set.
What we did is we created one more action to set the system status at the item level. After setting the system status at item level, header status also is getting set automatically.
Thanks.
Tej