Description: This area comprises all objects dealing with unit management. This introduction
provides an explanation of its basic structures.

For each unit type there is one general table and one table per hardware version.
E.g. there is the aimosRemoteUnitTable with objects that are valid for each
Remote Unit, and the aimosRemoteUnitV1Table with objects of the Remote Unit
Version 1. The general table contains one OID referring to the unit-specific
table.

Unit Reference
==============

The Index of the general tables is composed of the topological arrangement of
the units, i.e. depending on the arrangement it might contain several objects.
The Index of a general Remote Unit table entry (aimosRemoteUnitTable) is e.g.
composed of the Index of the Master Unit (aimosMasterID of type MasterID), the
Index of the SubRack Master Unit (aimosSubRackID of type SubRackID) and the
Index of the Remote Unit itself (aimosRemoteID of type RemoteID), since they
are arranged in this order, whereas the Master Unit itself only has one Index
(aimosMasterID), because there are no higher level units.

All unit-specific tables, however, are always identified by two objects, one of
the UnitReference type and the other of type ValueSource. Here, it does not
matter whether it is a Master Unit or a Remote Unit.

Value Source
============

The unit-specific tables have three entries per unit:
. one entry specifies the desired values
. one entry serves to read the current values and to buffer them for subsequent
  access
. and the third entry contains the buffered values

Which one of these three entries is to be accessed is specified with the second
Index of the unit-specific tables of type ValueSource.

To avoid that a GET BULK results in endless hardware accesses, the A.I.M.O.S. SNMP
Agent normally provides only the buffered values. Also, in case of a GET NEXT
only the table entry corresponding to ValueSource cachedValue(2) is returned.

Read accesses with cachedValue(2), however, are treated like accesses with
actualValue(1), if no buffered values are available or if the time stamp
belonging to these values was deleted.

ValueSource desiredValue(3) is to be used for write access. However, the
A.I.M.O.S. SNMP Agent also accepts write access to table entries with ValueSource
cachedValue(2). This is treated as if the write access was made with
desiredValue(3).

Values
======

The unit specific tables comprise objects containing various types of status
information. Due to performance reasons, values of the same 'topic' are put
together on a logic basis. Such logical object groups can be recognised by the
name. E.g. the aimosSubRackV1Table comprises the following objects regarding
attenuation:
. aimosSubRackV1AttenuationAge
. aimosSubRackV1AttenuationAmp1DL
. aimosSubRackV1AttenuationAmp1UL
. aimosSubRackV1AttenuationAmp2DL
. aimosSubRackV1AttenuationAmp2UL
. aimosSubRackV1AttenuationAmp3DL
. aimosSubRackV1AttenuationAmp3UL

These values are always dealt with together, i.e. if one of these values is to
be read directly by the Master Controller, all the other values will be read,
too. The time of this access is recorded in the age-object belonging to each
status group.

Time objects can be set to 0. This serves to prompt the A.I.M.O.S. SNMP Agent
to get the current values with the next access to a cachedValue(2)-instance.