When do I need to update the Report Model - reporting-services

Question

There is a constant change (!) in our database, new columns are often added.
Is reporting services the tool to choose for reporting in this case?
Case1: Developers add a new column to a table used in a report. Will the old reports created with a report model based on the old table still work?
Case2: Developers add a new column, and end users want to be able to report on it. If we update the report model, will the old reports based on the old report model still work? Or do we have to create a new report model every time the end user wants to report on a newly created column?
Regards
Lars

Answer 1

Reporting services has required strategies for change management. So, adding new column to a table in the underlying data source does not affect the reports.
If you want to include a newly added table column into your report model you should update (not create from scratch) your report model. Updating the report model automatically insert your new column to the model and does not break your old reports. on the other hand, updating report model does not update/delete the existing item if you change them (like table/column name or column data type etc) in the underlying source. You should manually change them at the report model and at the affected reports.
So, in your case, you won't be having any problem with reporting services.
Here i'm adding a change management section of the Reporting Services/Report Model document and strongly suggest you to read it.
Change Management
Models and the reports based on them
have many internal and external
dependencies. Therefore, you need to
consider the impact of changes
introduced into the dependency chain.
Report models based on relational data
sources use GUID attributes to
identify each entity, attribute, and
role. As mentioned, the report
model-generation process sets the
GUIDs, which are re-created at each
generation. For that reason and to
preserve edits on the report model,
generating a new report model each
time a change occurs is not an option.
You must work with the existing model
and update it, either manually or by
using the update options described
below.
The Semantic Query Engine
manages missing attributes when they
are not critical to report processing.
This functionality is in place to keep
reports running when security
attributes preclude users from seeing
some attributes in the report that may
be allowed to other users. Thus, if a
user is not allowed to access a field
such as the employee home telephone
number, the Employee Listing report
will run for that user but will not
show the excluded information. This
functionality works to your advantage
when models are edited to delete a
non-critical attribute. The report
will still run after you have removed
an attribute, although the report
might show a blank field. However,
query or report processing can be
broken by other changes to the model.
Remember that you should not overwrite
a model generated from a relational
data source when any reports depend on
it.
Schema Changes
If the underlying schema changes and
report model entities or attributes
are affected, you might have to update
the report model accordingly. To do so
in BIDS, use the Autogenerate command
on the Reporting Model menu. You can
also select Autogenerate from the
model item's context menu. By using
the context menu, you can select which
item on the model you want to update
without having to update the entire
model.
The autogeneration process will
show informational, warning, and alert
messages. These messages will show all
items in the model that are
out-of-sync with the underlying DSV,
even though those items are not
specifically included in the item
selected for autogeneration. This
functionality helps detect potential
errors than may lead to unpredictable
errors when running reports based on
the model.
Automatic update affects
newly added items only. The
autogeneration process will add any
new entity, attribute, or role found
in the DSV, but will not delete or
change any entity, attribute, or role.
Therefore, you need to manually manage
updated or deleted items. The messages
shown at the end of the generation
process will highlight any entity,
attribute, or role that needs to be
updated in the resulting out-of-sync
model. You will have to update the
model manually or revert the DSV
changes to maintain model-to-schema
coherence.
Data Source Changes
You can develop and test your model in
a development environment and then
deploy the model in a production
environment easily by changing the
connection string in the data source
file that the DSV uses. The two data
source schemas must be identical.
Note that the DSV contains statistics
based on the actual database data. As
mentioned in the section "Statistics
in Report Model Generation," the value
of those statistics will drive some
algorithm decisions during the model
generation. Therefore, if the
development database data is
significantly different from the
production database data, the model
might not be optimized for the data
that will eventually be used.
Hope this help.