Update: 5 Oct 2015
We have tested the release version of El Capitan (Mac OS X 10.11) and have ascertained that the data destroying bug has been addressed. However other issues have appeared, so if you choose to install El Capitan 10.11 on your server (and our advice is to wait for Apple to get a few bug fix releases out the door before you do), you must do the upgrade in the following order:
1. You must first update your Datacentre to MoneyWorks 7.3 before upgrading your server to El Capitan. This is accomplished by clicking the Check Now button on the Update tab of the MoneyWorks Datacentre console, as described above.
2. Once the Datacentre upgrade has been done you can upgrade your server to El Capitan (however you should first check that any other software you run is compatible—FileMaker for example will not currently run on El Capitan).
Original Post: 30 Sep 2015
The El Capitan full installer released today has a bug that will break MoneyWorks Datacentre server installations. Among other issues, the bug breaks Datacentre’s software update mechanism, so it is very important that you DO NOT install El Capitan on a Datacentre server. We are devising a workaround for the bug, which will be in the Datacentre 7.3 update.
It is important that you install Datacentre 7.3 before updating your server Mac to El Capitan.
This problem only affects MoneyWorks Datacentre (and possibly other server software). It is safe to install El Capitan on your other Macs. Of course you should never install a new OS without having a complete backup of your computer.