Re: net-snmp help required

On 3 February 2011 10:49, Imran Ali <[email protected]> wrote:
> However, I'm trying to ..... unload
> the shared object, and delete it from the "dlmodTable".
> I can do both of these things, however, "dlmodNextIndex", which is
> documented as being "the index number of next appropiate unassigned
> entry in the dlmodTable", remains unchanged. I would have thought it
> should decrement. Can anyone please shed some light on this matter?


No - it's more common to not re-use indexes.
If you load a new module, then it should get a new index - regardless
of what else has happened.   This is less likely to cause confusion
with client applications.

Consider the following scenario

A client application queries the dlmod table
       entry 1 = John module
       entry 2 = Paul  module
       entry 3 = George  module
       entry 4 = Ringo  module
             and caches this information

You unload the "Ringo" module (entry 4 unused)
and then load the "Bert" module

Suppose the client application then checks the
status of the modules that it knows about.

It you are assigning the "lowest available" index,
(allowing index re-use) then  entry 4 will be the
new "Bert" module, but the client application assumes
that this is "Ringo".

If you do *not* re-use index values, then the Bert
entry will be given an index of 5.
When the client application queries the value of status.4,
it will be told "noSuchInstance", and will then know that
something has happened to Ringo.


In general, it's considered good practise to not re-use
arbitrary indexes (at least, not until you run out!)
If you think about it, that's also how process IDs work.

Dave

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