When starting an opcua server, the creation of the address space is
currently a performance bottleneck. The startup process can be accelerated
by loading a pre-generated address space pickle.
However, the startup process still takes ~25 seconds on a raspberry pi
model b (compared to ~125 seconds when generating the address space from code).
Storing the address space in a shelve, where the data for each node is
pickeled individually, allows to further improve the startup performance
since only the nodes that are actually accessed are loaded from
disc (all other nodes are loaded later when they are accessed).
Since the default address space contains thousands of nodes but just a
small amount is actually accessed during startup, the startuptime could
be improved to ~3.5 seconds.