Cause

Description

Users get padlock cursor when saving or posting, turn off computer

Or,

a user's computer freezes, gets restarted

This is one of the most common causes of data damage, because users misunderstand the meaning of a "padlock" cursor. During data-entry or saving, the "pointer" cursor becomes a "padlock" when the same file is use by some other user, whoever got it first. This is a natural feature of record-locking multi-user databases, and occurs to ensure that two people don't edit the same record at the same time. The padlock cursor disappears automatically as soon as the person who's editing the record saves their changes, usually within seconds. But there's no way to know how long the user will keep it locked while making their changes. If the user with the padlock cursor thinks their computer has crashed and restarts it, the files being updated can be corrupted. To prevent data damage, every user should know not to restart their computer while saving. Padlocks can be canceled by pressing command-period (on a Mac) or control-break (on a PC).

Disk fragmentation on the server's hard drive

Disk fragmentation can cause the file server to save data in irregular locations on the hard drive, making it more difficult for Clients & Profits to efficiently find the data when it's requested by users. Over time, sections of the C&P database end up being spread all over the hard disk, making it vulnerable to disk directory errors.

Power problems (surges, failures, brownouts, etc.)

Power failures can cause the corruption if data is being saved in the C&P database incompletely (it's as if all of the current users restarted their computers; see above). Power surges and brownouts can cause data to be saved erratically in the Clients & Profits database, making some records partially unreadable or otherwise unusable.

Bad RAM, network adapter, or other hardware on the server

Faulty hardware, defective network adapters, and other equipment problems can cause data to be saved incorrectly into the Clients & Profits database, making those records unreadable. Since hardware problems like this start sporadically, then gradually get worse, you'll see an increasing amount of data corruption until the problem is discovered and fixed. The best way to troubleshoot hardware problems is to selectively replace one component at a time until the faulty one is found. These are the toughest problems to troubleshoot.

Poor LAN wiring, loose connectors, electrical interference from heavy equipment

Low-quality network cables can cause signal loss, which forces the workstation to resend the same data several times before it is successful. Loose LAN connections can cause erratic communication with the server (which appear to the user as a padlock cursor). Frayed or pinched wiring, as well as cables that are walked on, can cause problems over time as the cables degrade. Unshielded cable laid next to elevators, large copiers, and other electrical equipment can cause intermittent communication errors, which can make a user think their computer has frozen or crashed, so they reboot it, breaking their server connection to the database.

Faulty system software, software incompatibilities, driver conflicts; excessive heat in the server room; disable opportunistic locking in WinNT

On the server side, faulty system software, incompatibilities and conflicts can cause crashes that suddenly disconnect users from the C&P database. The data files and header blocks being updated when the server crashes can then become corrupted. If the server's hard drives become too hot, data possibly won't be saved correctly. In high-volume shops, disabling "opportunistic locking" on the Windows NT file server will better tune the server for databases.

Too much server traffic; server caches set too high, so small data packets aren't written to disk

In shops where one server is being shared for both graphics and administration, the high traffic generated by moving graphic files can overwhelm the server and cause performance problems for Clients & Profits users. If the server slows down so much that C&P users think they've frozen, they're likely to reboot their computers, breaking their connection with the C&P database, which can damage it. It's highly recommended that admin have its own file server.

Windows 95/98 write-back cache not disabled, VERIFY not enabled

The "write-back" cache in Windows 98/XP is enabled to improve performance, but it interferes with network applications like Clients & Profits. The cache keeps C&P data from being saved to the file server, causing data corruption. Enable the VERIFY command. For more info, see Windows Tips.