Usage of multiple PDP context

[Chraebs]

Hi

As there are 12 PDP context available on nrf9160, I was wondering about the correct usage of them.

Usually, my use case involves only 1 context (cid=0). I configure it with the Access Point Name defined by my SIM provider (e.g. `AT+CGDCONT=0,"IP","my-apn`) and I'm good to go to get the IP address. This step is even optional in case that the service provider configured the default one correctly.

The information from 3GPP 27.007 Ch. 10.1.1 do not really show me a use case of having multiple context:

Description
The set command specifies PDP context parameter values for a PDP context identified by the (local) context identification parameter, <cid> and also allows the TE to specify whether security protected transmission of ESM information is requested, because the PCO can include information that requires ciphering. There can be other reasons for the UE to use security protected transmission of ESM information, e.g. if the UE needs to transfer an APN. The number of PDP contexts that may be in a defined state at the same time is given by the range returned by the test command.
For EPS the PDN connection and its associated EPS default bearer is identified herewith.
For 5GS the PDU session and its associated QoS flow of the default QoS rule is identified herewith.
A special form of the set command, +CGDCONT=<cid> causes the values for context number <cid> to become undefined.
If the initial PDP context is supported, the context with <cid>=0 is automatically defined at startup, see subclause 10.1.0. As all other contexts, the parameters for <cid>=0 can be modified with +CGDCONT. If the initial PDP context is supported, +CGDCONT=0 resets context number 0 to its particular default settings.
The read command returns the current settings for each defined context.
The test command returns values supported as compound values. If the MT supports several PDP types, <PDP_type>, the parameter value ranges for each <PDP_type> are returned on a separate line.

Questions:

1. Is overwritting the initial context (cid=0) the correct/recommended way to the the APN?
2. Can you describe some use cases for having multiple PDP context (or reference some further reading on it)?

Thank you!
Matthias

[Chraebs]

After reading through all related forum entries another time, I found that the answer by Didrik in [1] contains answers that are related to my questions.

Regarding question 1:

CID 0 is used during the attach, while CID 1 (or others) can be used to open additional PDN connections after the initial attach.

Regarding question 2:

However, if this is allowed, or what they can be used for depends on the network.

[1] https://devzone.nordicsemi.com/f/nordic-q-a/69326/multiple-apn-setting-on-nrf9160