Rewritten April 2015

In a peer-to-peer (P2P) network environment, A-Shell/Windows uses the computer name to establish a unique ID for each session. The computer name is sometimes referred to as the Machine Name and can be found and set in the My Computer System Properties dialog. It is critical that each workstation on the network has a unique Computer Name, although it is unfortunately common for installers to overlook this step when installing new machines.

When a new A-Shell session is launched, it scans the job table to see if there is an existing record for this machine/instance, and if so, it assumes that the prior session was terminated uncleanly, such as by rebooting the PC, and re-uses that same job table record so as to avoid accumulating orphaned job table entries. If there are multiple machines with the same name, A-Shell will be fooled into thinking that a new and distinct session is actually a restart of a previously aborted one, causing the earlier session's job table record to be overwritten. This is likely to lead to the first session aborting with a cryptic "your job table has been zapped" message. Outside of A-Shell, the duplicate computer names will cause a variety of other problems that are best avoided.

To help identify this error before it becomes a more serious problem, A-Shell (see History, below) generates its own unique identifiers for each machine during installation; it can then use that information to identify duplicate machine names when new sessions are launched, thus allowing the problem to be detected and resolved right away. In order for this to work, you must run the installer/updater to update each workstation, rather than manually installing the update by copying files.

The installer/updater establishes a unique identifier for each machine and saves it in the HKLM section of the registry, to be used to determine whether an instance with the same machine name as an existing instance is actually the same machine or not. If so, then the new instance can safely overwrite the old one. But if not, an error message is displayed and the new session is not allowed to start.

The error message will indicate the machine name, the user name and jobname of the offending existing instance, and the unique identifiers (8 hex digits) for the two machines. You can use the SYSTAT/CU switch to display the unique identifiers for existing sessions, which may be helpful in tracking down the offending duplicate-named machine.

Also note that the issue only affects P2P networks; ATE, Terminal Server, and UNIX systems are not subject to the problem and are not affected by the update.

History

2015 April, A-Shell 6.1.1408:  A-Shell now detects duplicate machine names.