Hello,

I use dmcc java sdk to design an application from where we can create a session for registering stations and pressing a button, then unregister, but keep the session.
Please, what is the max concurrent registration requests allowed in this case?

Is your question
1) how many sessions can be active, or
2) how many active registrations per session, or
3) how many inactive registrations (i.e. DeviceIDs) can a single session have?

it is #2:
2) how many active registrations per session

The answer varies by release of AE Services. It can be found in the 'capacities' section of the AES Overview document for that release

https://www.devconnectprogram.com/site/global/products_resources/avaya_aura_application_enablement_services/releases/8_1_3/index.gsp#tabs-product-downld-2

For 8.1 the maxima is 8,000 active DMCC device registrations per session. However, there are considerations use of encryption, use of server media, and how frequently can a registration be done for one), is dependent on other factors which need to be taken into account in any application that scales. So what you will achieve in your environment requires more careful examination of the system configuration than can be done through a forum exchange.