• If you choose COP -> Processing -> Print Invoice, the system will lock the COP Lock File (CPLCKFIL.DAT in DATA folder).  COP Lock File is a way to tell other users to stay out of invoice printing to prevent potential conflict.  With the way the batch invoice printing code is written, the system must do this to prevent conflict. Other Accounts Receivable application will also create the lock file. These include: Sales & Dr/CR Memo Processing and Service Invoice Processing.
• On the other hand, if a user is performing invoice printing from shipping verification, this type of printing one invoice at a time will not lock the COP Lock File.  But the system will check to see if the COP Lock File is locked.  If it is, you will get this error.

So the conclusion is you can have multiple users performing the “Print One Invoice” (printing invoices through Shipping Verification) type of processing simultaneously.  But as soon as a user chooses to print batch invoices (COP -> Processing -> Print Invoice), it will lock other users from invoice printing.  So whoever performs batch invoice printing needs to watch out for the timing and make sure to exit immediately when done.  If you should receive this error, you can find out who lock the CPLCKFIL.DAT by referring to the following KB article:

    https://support.netcellent.com/portal/en/kb/articles/how-to-fix-cop-lock-file-error-when-printing-invoice

The following are areas in Elliott that can perform the "Print One Invoice" function without locking up the COP Lock File:

• COP Billing Selection -> Print Immediately Invoice
• Order Entry to enter "I" or "C" type of order -> Print Immediately Invoice
• Shipment Confirmation -> Print Immediately Invoice
• Sales Desk -> Print Invoice (Point of Sales mode)
• Shipping Verification -> Print Invoice
• Print One Invoice
• Print Duplicate Invoice from Invoice History