getting error in sqlite DB Error: unknown error in ios 8

I am using sqlite DB to save data.i want to save apps state lifecycle of the app. for that i used sqlite .i have created table with two colums . i am i am able to save data also. but some time i am getting this error DB Error: unknown error .

**DB Error: unknown error**

Could not execute the query.

-(void)saveInfo{

    // Prepare the query string.
    NSString *query = [NSString stringWithFormat:@"insert into processInfo values(null, '%@', '%@')", _timeFormatter, _process];

    // Execute the query.
    [self.dbManager executeQuery:query];

    // If the query was successfully executed then pop the view controller.
    if (self.dbManager.affectedRows != 0) {
        NSLog(@"Query was executed successfully. Affected rows = %d", self.dbManager.affectedRows);


    }
    else{
        NSLog(@"Could not execute the query.");
    }

}


- (void)dateAndTime {
    if(!self.dateFormatter) {
        self.dateFormatter = [[NSDateFormatter alloc] init];
    }
    [self.dateFormatter setDateFormat:@"yyyy-MM-dd hh:mm:ss"];
}

//call back
static void displayStatusChanged(CFNotificationCenterRef center, void *observer, CFStringRef name, const void *object, CFDictionaryRef userInfo)
{
    // the "com.apple.springboard.lockcomplete" notification will always come after the "com.apple.springboard.lockstate" notification
    CFStringRef nameCFString = (CFStringRef)name;
    NSString *lockState = (__bridge NSString*)nameCFString;
    NSLog(@"Darwin notification NAME = %@",name);

    if([lockState isEqualToString:@"com.apple.springboard.lockcomplete"])
    {
        NSLog(@"DEVICE LOCKED");


        //Logic to disable the GPS
    }
    else
    {
        NSLog(@"LOCK STATUS CHANGED");
        //Logic to enable the GPS
    }
}

-(void)registerforDeviceLockNotif
{
    //Screen lock notifications
    CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(), //center
                                    NULL, // observer
                                    displayStatusChanged, // callback
                                    CFSTR("com.apple.springboard.lockcomplete"), // event name
                                    NULL, // object
                                    CFNotificationSuspensionBehaviorDeliverImmediately);

    CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(), //center
                                    NULL, // observer
                                    displayStatusChanged, // callback
                                    CFSTR("com.apple.springboard.lockstate"), // event name
                                    NULL, // object
                                    CFNotificationSuspensionBehaviorDeliverImmediately);
}


- (void)applicationWillResignActive:(UIApplication *)application {


    NSLog(@"\t ----- App will tResignActive  %@ -------",[self.dateFormatter stringFromDate:[NSDate date]]);

}

- (void)applicationDidEnterBackground:(UIApplication *)application {


     NSLog(@"\t ----- App in Background  at %@ -------",[self.dateFormatter stringFromDate:[NSDate date]]);


    _timeFormatter=[self.dateFormatter stringFromDate:[NSDate date]];
    _process=@"Background";
    [self saveInfo];


    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
    // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}

- (void)applicationWillEnterForeground:(UIApplication *)application {


     NSLog(@"\t ----- App in Forground %@ -------",[self.dateFormatter stringFromDate:[NSDate date]]);

    _timeFormatter=[self.dateFormatter stringFromDate:[NSDate date]];
    _process=@"Forground";
    [self saveInfo];


}

- (void)applicationDidBecomeActive:(UIApplication *)application {

     NSLog(@"\t ----- App will tResignActive  %@ -------",[self.dateFormatter stringFromDate:[NSDate date]]);


    [self saveInfo];


}

- (void)applicationWillTerminate:(UIApplication *)application {


    NSLog(@"\t ----- App will terminate %@ -------",[self.dateFormatter stringFromDate:[NSDate date]]);

    _timeFormatter=[self.dateFormatter stringFromDate:[NSDate date]];
    _process=@"terminate";

    [self saveInfo];

}