It 'would' appear that using VBIsam files does not allow sharing between programs.
I have attached two sample programs - one .exe & one .dll.
The .exe creates an Isam file - writes records - closes the file - reopens 'shared' & reads a record.
Then the second program is 'called' which opens 'shared' the same file and--
'is supposed to read the same record' (the key is passed from the first program) and then read the
next record.
The second program crashes with status 61 - file sharing conflict.
This works when running the programs when BDB is the Isam handler.
Attached - 2 sample programs + .trx (trace of failure) - + cobc command lines. Windows 10.