When working with adapters on multiple hosts group (or in a cluster), keep in mind that enabling an adapter (especially SQL Adapter) perform the command (Select or Stored procedure) on every host at the same time and can cause a race condition.
While FTP, MSMQ and POP3 adapters are listed in the guide to be clustered (and not grouped) the SQL adapter is not listed and therefore can be groups – and will be running on every host.
In this case, the SP road should be taken (and not Select directly from the table) and implementation of locks should be executed in the SP.
See http://msdn.microsoft.com/en-us/library/cc507804.aspx for more details (Recommendation 5).
Shimshon
