# Control of LCM operations over a NS instance #

## Proposer ##
- Gerardo Garcia (Telefonica)
- Alfonso Tierno (Telefonica)
- Francisco Javier Ramon (Telefonica)

## Type ##
**Feature**

## Target MDG/TF ##
NBI, LW-UI, osmclient

## Description ##
The set of operations that can be done over a NS instance is the following:
- Initiate
- Update
- Scale
- Terminate
- Action/primitive

While running an operation over a NS instance, other operation calls might
arrive to OSM and a mechanism is necessary to control how to deal with these
coming operations while in the middle of a previous transaction.

Since most probably there will be several consumers of the NBI, the natural
mechanism is not allowing an operation to be executed if another operation
arrives in the middle of the transaction. The LCM module will be in charge of
that since it is the module involved in all LCM operations over a NS,
originated from both NBI or other internal modules.

There is a special case that should be handled in a different way: the
"terminate" operation. In this case, two behaviours are possible:
- Reject the operation while in the middle of a previous transaction
- Force the termination of the NS instance, forcing the end of previous
transactions.

An appropriate modeling of the NB API call should allow both cases.

## Demo or definition of done ##
This demo could work:
- A first action will be executed over a NS instance. It will succeed.
- A second action will be executed while in the middle of the transaction. It
will fail. The status could be checked from the NBI (LW-UI and client)