Why am I getting 'Failed to chmod' on Android?

I'm getting the warning messages 'Failed to chmod' and 'chmod failed: EPERM (Operation not permitted)' when I execute my app on my Android phone. The code below occurs them.

SQLiteDatabase db = openOrCreateDatabase("/sdcard/my_data.db", MODE_PRIVATE, null);

1. With a path like above, I get the warning. But without a path, no warning.

2. Warning with my phone, but no warning with Genymotion.

3. Even though the warning occurs, the app works fine.

4. My phone is Samsung Note2 and the android version is 4.4.2. The android version of the emulator is 4.3.

May I ignore the warning?