If you have an earlier version of one of the Communications Suite products installed in Schema version 1 mode, and want to install a second product, you might be tempted to avoid migrating your Schema version 1 mode LDAP to a Schema version 2 mode. If so, consider the following facts:
For Schema version 1 mode, there is not one unified tool to use for user, group, resource and domain administration.
For Calendar Server, only command-line utilities are available, no GUI.
For Messaging Server, there are three separate tools used, a command-line utility, a GUI (iPlanet Delegated Administrator) and the Administration Server Console. None of these tools support Calendar Server. In Communications Suite 5, the latter two are deprecated and are no longer included in the distribution.
While it is possible to run both products in Schema version 1 mode, it places a lot of burden on the system administrators to keep it all straight and avoid deleting something the other product needs.
Schema version 1 based Calendar Server administration utilities allow entries to be fully deleted (purged) from LDAP without regard to another product's dependence on the entries. Thus, the administrator must be responsible for the integrity of the LDAP for both products. The administrator of a deployment of two products using Schema version 1 might find it difficult to avoid inadvertent purges or unwanted changes to a user's LDAP record. For the same reason, you should not attempt to have both a Schema version 1 mode product and a Schema version 2 mode product share the same LDAP.
Keeping your older Calendar Server deployment in Schema version 1 non-domain mode is no longer possible. Calendar Server 6.3 software automatically converts Schema version 1 non-domain configurations to multiple domain mode by creating a single default domain under the root at configuration time and assuming all non-fully qualified uid's imply the default domain. For Calendar Server 6.3, you can't avoid multiple domain mode.
Access Manager won't work with a Schema version 1 LDAP entries.
To Use Schema version 2 in either mode and its administration tool, Delegated Administrator, you must have Access Manager installed in legacy mode.
For Schema version 2 modes, there is one unified tool, Delegated Administrator Console (GUI) and its command-line utility equivalent, commadmin. You can administer both Calendar Server and Messaging Server domains, users and groups with these tools. Using a Delegated Administrator interface for both services, prevents an administrator from inadvertently deleting another service's LDAP entries.
If you plan to use Access Manager, you must choose one of the Schema version 2 modes for both Messaging Server and Calendar Server deployments.