If the physical structure of your system can be split into ‘modules’ and you intend using Group Templates and Group Instances to configure those modules, you will need to consider:
How many different ‘modules’ exist on your system
You will need to add one Group Template for each different ‘module’. (Remember that if ‘modules’ only differ slightly—say in the number or type(s) of point that each module contains—it may be possible to use Abstract Items to produce the ‘base’ configuration for those items. Using Abstract items can avoid the need to produce multiple Group Templates.) Ensure that you are aware of any Limitations and Restrictions.
The content of each of Group Template
You will need to decide on the number and type of ‘core’, driver-specific, and/or Abstract items that you need to include in each Group Template. Each of these items will be replicated in each Group Instance that references the Group Template.
The complexity and size of the Group Template and Group Instance configuration
Geo SCADA Expert automatically propagates any Group Template changes to each Group Instance that references the Group Template. During this time, access to the database is prevented (see Activities that are Restricted when Configuration or Structure Changes are Pending). With large or complicated Group Template and Group Instance set-ups, there may be a noticeable period for which access to the database is prevented while the server propagates the changes. (If fewer than 100 Group Instances reference each Group Template, the time for which the database is ‘locked’, if noticeable, only comprises a few seconds.)
Which Properties are to be Optional or Unique
You will need to decide which configuration properties are to be optional or unique to each database item in the Template. (You use the Property Overrides feature of the Group Template to specify which properties are derived from the Template and which can be overridden locally, on a per-item basis in each Group Instance.)
Naming Convention
Remember that the name that you give to an item in a Group Template is replicated in each Group Instance that references that Template. You cannot rename an item in a Group Instance directly—you can only rename an item in a Group Template. (The exception is an item that has been added locally to a Group Instance (not recommended).) You therefore need to decide on a suitable naming convention for the items that appear in your Templates and Instances (taking into account the Geo SCADA Expert Naming Restrictions).