I am beginner of iPhone I have created database but that give run time error of Failed to create writable database file with message 'The operation couldn’t be completed

my code is

-(void)createdatabase
{
    NSFileManager *fileManager=[NSFileManager defaultManager];
    NSError *error;
    NSString *dbPath=[self getDBPath];
    BOOL success=[fileManager fileExistsAtPath:dbPath];
    if(!success)
    {
        NSString *defaultDBPath=[[[NSBundle mainBundle]resourcePath] stringByAppendingPathComponent:@"SQL.sqlite"];
        success=[fileManager copyItemAtPath:defaultDBPath toPath:dbPath error:&error];
        if(!success)
        {
                NSAssert1(0, @"Failed to create writable database file with message '%@'.", [error localizedDescription]);  
        }

    }
}

give any suggestion and source code which is apply in my code