After you have finished making the changes, you must tell your users what you have done. Again, this should be a summary of the previous messages (invariably someone will not have read them.)
However, there is one important addition you must make. It is vital that you give your users the current status. Did the upgrade not go as smoothly as planned? Was the new storage server only able to serve the systems in Engineering, and not in Finance? These types of issues must be addressed here.
Of course, if the current status differs from what you communicated previously, you should make this point clear and describe what will be done (if anything) to arrive at the final solution.
In our hypothetical situation, the downtime had some problems. The new CPU module did not work; a call to the system's manufacturer revealed that a special version of the module is required for in-the-field upgrades. On the plus side, the migration of the database to the RAID volume went well (even though it took a bit longer than planned due to the problems with the CPU module.
Here is one possible announcement:
The system downtime scheduled for Friday night (refer to the System Administration page on the company intranet website) has been completed. Unfortunately, hardware issues prevented one of the tasks from being completed. Due to this, the remaining tasks took longer than the originally-scheduled four hours. Instead, all systems were back in production by midnight (6am Saturday for the Berlin office).
Because of the remaining hardware issues, performance of the AP, AR, and the Balance Sheet report will be slightly improved, but not to the extent originally planned. A second downtime will be announced and scheduled as soon as the issues that prevented completion of the task have been resolved.
Please note that the downtime did change some database indices; people that have written their own SQL queries should consult the Finance page on the company intranet website.
Please contact System Administration at extension 4321 with any questions.
With this kind of information, your users will have sufficient background knowledge to continue their work, and to understand how the changes impact them.