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Avatar of lal_delphi
lal_delphi

Lock Timeout
Our in-house software consists of Delphi 2 applications running on a Novell network using Paradox tables with v5.1 BDE. The applications are rather data-intensive with multiple client directories and over 80 tables per directory (some 100mb+). Only one client directory is accessed at a time within an application but mutliple applications run on the same computer can access that directory. Multiple users can also access the same directory. Currently up to 25 users can be using the system. This is not client/server software.

All of the sudden we are having problems with Lock Timeouts. These can occur when a table is being opened or during processing. There are no table locks involved.

Other factors that may or may not be involved:
  Multiple instances of tables can be open
  TDatabase component used to switch to different client directories (open/close to switch)
  Remote users are logging through a Citrix server
  Recently (but after timeout problems) upgraded BDE from v4.x

Some things we have tried include:
  Upgrading the BDE
  Setting the Session PrivateDir to the users' local harddrive for sql lock files
  Setting the Session LockRetry to a greater number

Lock files seem to be a mystery with the program having little control over them. The easy answer is to upgrade Delphi and use a different database but other factors at this moment prevent that. What can cause lock timeouts; can you programatically trap or prevent them?

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Avatar of YodaMageYodaMage

You have two applications accessing the same table. Delphi puts a write lock on tables while checking to see if table is opened for exclusive use. App1 Locks table rather you like it or not while checking for .lck's, then app2 accesses the table and also applies a tempory lock while it analizes and opens the table.

When app1 tries to release its' lock, BOOM, it cannot because of the lock applied by the second application.

You can try adding:

Check(DbiSetLockRetry(5))

to your code.
Avatar of lal_delphilal_delphi

ASKER

Your explanation of what's happening with the lock files makes some sense. But, to clarify, are you saying that multiple sessions/users can put locks on the same table but one can't release their lock if another session/user has placed a lock? That doesn't seem right.

We've already tried Check(DbiSetLockRetry(5)), even with a larger value since 5 is the default value.
ASKER CERTIFIED SOLUTION
Avatar of YodaMageYodaMage

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Delphi

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Delphi is the most powerful Object Pascal IDE and component library for cross-platform Native App Development with flexible Cloud services and broad IoT connectivity. It provides powerful VCL controls for Windows 10 and enables FMX development for Windows, Mac and Mobile. Delphi is your choice for ultrafast Enterprise Strong Development™. Look for increased memory for large projects, extended multi-monitor support, improved Object Inspector and much more. Delphi is 5x faster for development and deployment across multiple desktop, mobile, cloud and database platforms including 32-bit and 64-bit Windows 10.