Hi,

I'm realy wondering if you don't have already a defined process design kit
with a popper techfile in your design environment.
If so you should use it or use it at least as reference.

For techfile examples
check your Cadence DFII installation directory
<installDir>/tools/dfII/samples/techfile
or go to
http://pdk.cadence.com
and sign up, they have a generic PDK for free.
You can also dump the techfile of the 'cdsDefTechLib' as a start point
to create your own.

To the questions:

> If just for a layout databade stream-in and display,
> I can only use the layer definition, and I don't need the device definition and layer rule definition,
You need at least
layerDefinitions(
  techPurposes( ... )
  techLayers( ... )
  techLayerPurposePriorities( ... )
  techDisplays( ... )
)
and
layerRules (
  streamLayers( ...)
)
or a layer mapping table

> especially there are layerMfgResolutions and layerRoutingGrids in the layer rule, are these important?
This are technology file setting for the Cadence Custom Router  and they are not needed if  you
do not use this tool.
But I think 'physicalRules( mfgGridResolution( ... ) )' should be used.

> In my opinion, the layer rule specifies the minimum spacing which is similar to the DRC rule,
> what is purpose for these layer rule?

The 'layerRules(...)' section most common usage is the subsection 'streamLayers( )' which defines
the mapping between DFII layer names and GDSII layer numbers.
But if you mean the
'physicalRules( ... )' there are the subsections 'spacingRules( )' and 'orderedSpacingRules( )'
which are defining the default spacing, width and enclosure for most of the DFII layout tools
like Virtuoso and VirtuosoXL etc.
 
> what is the formation of the layer mapping table
#  Layer        Layer      Stream   Datatype
#  Name         Purpose
#--------------------------------------------------------------------
  myLayerName         myPurpose        1       0
> should I put it at "User defined data"?
Yes

> BTW, should the layer number in the techfile be the same as that in the Input-layer description of the DRC and LVS rule file,
In general you foundry defines the configuration of the GDSII layer numbers.
Then there are layer numbers in
layerDefinitions( techLayers( ) )
and in
layerRules( streamLayers( ) )
which can be same to keep the order, but this is not absolute must.

> Can I choose this layer number at will?
See above.

Bernd