The OnTime Group Calendar server task listens to events on the Domino servers being monitored in order for OnTime Group Calendar to synchronize calendar entries from mail files. Part of this process is discovering the replica ID of the databases to support OnTime clustering among other things. To discover the replica ID the OnTime Group Calendar server require access to the databases even though they may not be a mail database or an OnTime Group Calendar system database.

See a message similar to the following means that the OnTime Group Calendar server does not have access to the listed database:
OnTime-server01: WARNING: CN=Server01/O=OnTime!!IBM_ID_VAULT\MyIDVault.nsf: You are not authorized perform that operation

To not see the message the OnTime Group Calendar should have at least “No access w/ read public documents” access to the database. With this low access OnTime Group Calendar can discover the replica ID without having access to contained data.