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+# 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)