An error occured while attempting to initialize the Borland Database engine (error $2501)

Step 1 -  Log in using administrator

Step 2 - Go to Control Panel - BDE Administrator

Step 3 - under Configuration tab , select configuration - system - INIT

    change SHAREDMEMLOCATION : 2000 ; LOCALSHARED : TRUE; LOWMEMORYUSAGELIMIT : 64;     

    MAXBUFSIZE : 4096; SHAREDMEMSIZE : 4096

Step 4 -  restart Firebird

Solution 2:

If you failed to save the setting using BDE Administrator,

 example after click apply setting but BDE Adminstrator showing not responding, then can use the below alternative:

-go to registry editor, under HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Borland\Database Engine\Settings\System\INIT, choose the item you want to edit, right click and modify it.