appDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
NSArray *urlArray = [[NSFileManager defaultManager] URLsForDirectory: NSDocumentDirectory inDomains: NSUserDomainMask];
NSURL *documentsUrl = [urlArray firstObject];
NSError *error = nil;
BOOL success = [documentsUrl setResourceValue: [NSNumber numberWithBool: YES]
forKey: NSURLIsExcludedFromBackupKey error: &error];
if(!success){
NSLog(@"Error in disabling %@ from backup %@", [documentsUrl lastPathComponent], error);
}