iphone 6 - Do not disturb

Here is the description of do not disturb:

Use Do Not Disturb on your iPhone, iPad, or iPod touch - Apple Support

It's not clear what you're asking about when you reference "only while iPhone is locked." This means whatever do not disturb rules you have set up will only be in effect while the iPhone is locked. At other times, your iPhone will ring or buzz.

You have to answer these questions to use Do Not Disturb:

• Do I want to use this at all?
• If so, who shall I allow to override the Do Not Disturb?
• And, if I am using Do Not Disturb, is it in effect always or only while the iPhone is locked?

No.

Setting "only while iPhone is locked" dictates the silence time.

You do not also need to set a silent mode.

This is descrlived both in the article and in Settings.

If you always want to receive calls, just set:

• Settings > Do Not Disturb > Manual = "Off", and
• Settings > Do Not Disturb > Scheduled = "Off"

Then the Silence setting doesn't matter!