If you have problems running Modulus, often the cause will be hardware or system software failings. The following points commonly arise.

Memory issues to check:

That on a 68k Mac Client or Single-user Gold machine, you have at least 16 megabytes of total RAM (12,000 allocated to Modulus or the Client software as the preferred size in the Get Info window)

That on a 68k Mac Server you have at least 20 megabytes of total RAM (16,000 allocated to the Server software in the Get Info window)

That on a Power Mac Client or single-user Gold machine you have at least 20 megabytes of total RAM (16,000 allocated to Modulus as the preferred size in the Get Info window)

That on a Power Mac Server you have at least 24 megabytes of total RAM (19,000 allocated to the Server software in the Get Info window)

Although there is no substitute for real RAM, RamDoubler can be used with Modulus.

Virtual Memory cannot be used on most Macs.

On Systems where there is a shortage of RAM, sometimes as much as 3 megabyte can be freed for applications such as Modulus, merely by using the Extensions Manager Control Panel to switch off the unnecessary Control Panels and Extensions installed by default by the Macintosh System Software installers. Below is a typical list of the minimum set of System items needed to run most Macs.

Extensions: RAM Doubler (if installed), 040 VM Update (if you have an 040-based 68k Mac), 630 SCSI Update (if using a Macintosh Quadra/Performa 630), aLoadIDE (if present), Apple CD-ROM (if you have a CD drive), AppleShare (if connected to a network), File Sharing Extension, Foreign File Access (if you have a CD), LaserWriter - including 8 or 8.3 (if you are printing to a laser printer), Print Monitor.

Control Panels: Apple Menu Options, Date & Time, General Controls, Macintosh EasyOpen, Memory, Mouse, PC Exchange.

System Folder: Load RAMDblr (if installed).

In the Memory Control Panel both Virtual Memory and Modern Memory Manager should be turned off, and the Disk Cache should be set to no more than 512k.

On client machines in multi-user sites, if you have upgraded your version of Modulus or you are having problems that other users are not also experiencing, then it is a good idea to 'throw away the res and rex'. Open your System Folder, locate the Preferences folder, open the ACI folder found within. Delete (by dragging into the Wastebasket and then choosing Empty Wastebasket) the files ending '.res' and '.rex' and the folder name with the same prefix - which will be 'Modulus 4r2' or similar.

Networking: By preference Classic Networking should be replaced by Open Transport. However, some versions of Open Transport that came with some versions of the Mac OS do not work reliably with 4D databases (such as Modulus). The currently recommended System software is either 7.5.3 revision 2, or System 7.5.5, which have the correct versions of Open Transport.

If you cannot connect to the Modulus server, or lose your connection in use, physically check all network connections. Check whether other network services are available (your network printer in the Chooser, for example). Check that any routers are operating correctly.

Mac OSX is still very new and is still being tested with Modulus, although several Modulus sites are successfully using it.