I have develop a mobile app, which is using database. My problem is that when anybody uninstall app, database also uninstall. I want to mark my app as system app, so that nobody can uninstall it. User can use the app but can’t uninstall the app.
please guide.
Thanking you
This would certainly not be allowed. These devices go to a lot of trouble to make sure apps cannot abuse the device - an app which cannot be deleted could certainly cause trouble.
If you’re worried about the database being deleted if the app is deleted, you’ll need to keep a backup of the database on a server someplace.
Yes, We can keep backup of database on server, but the problem is that where user is using mobile, internet is not available. When user come in range of internet, he transfer data on server. My problem is that if app uninstall by user between working time and the time when he reached at internet range, then we loss full day working.
Are you using PhoneGap to create your app? If you are then two things:
You can store the actual app.apk file in the internal memory (or SD Card) and therefore reinstall it whenever and wherever you like.
You can save the database anywhere on your internal memory (or SD Card) and it won’t be deleted if/when the app is uninstalled.
To be honest I can’t even begin to imagine why your app would continuously be uninstalled if it’s actually required, but there are apps out there that can prevent other apps from being uninstalled. I don’t know if I’m allowed to advertise other products here, but if you search online you’ll come across parental apps that allow you to restrict certain aspects of the phone unless you have a password. I use one on my son’s phone and I can restrict just about everything on it, including the ability to uninstall apps.
Hope this helps. 
I need to reply to my own post to mention that the above is true for Android devices.
If you are using iOS devices then I believe there’s not much you can do. 