shared memory already created error

[Hamish Moffatt]

We use Firebird embedded in our two Windows applications. Users may
sometimes have both applications open at once connected to the same
database, which is working as we have configured Firebird (5.0.1) to use
SuperClassic mode.

We have only recently upgraded this application from Firebird 2.5.9.

We have a report of an error connecting to the database:

Shared memory area is probably already created by another engine
instance in another Windows session (335544984)


What causes this error? What is "another Windows session" in this context?


thanks,

Hamish

[Vlad Khorsun]

  About "Windows Session" - unfortunately I failed to find good and clear documentation by MS, 

looks like they moved or removed old MSDN articles. Below is useful links that I found today:

http://jdebp.info/FGA/windows-nt-session.html

https://stackoverflow.com/questions/4686897/sessions-window-stations-and-desktops

(see point (2) at the asnwer)

https://learn.microsoft.com/en-us/windows/win32/termserv/terminal-services-sessions

  The issue happens when one process tried to create named kernel object (file mapping in our case)

while another process running in another session already created such object. If both processes 

uses own Local namespace - it is prohibited as there could not be two diferent kernel objects for the

same physical object (disk file that is mapped into memory). See

https://learn.microsoft.com/en-us/windows/win32/termserv/kernel-object-namespaces

  Firebird 5 uses private namespaces, when possible, so such error should not happens. 

Any info in the firebird.log ?

Regards,

Vlad