After upgrade to BIOVIA Workbook 2021 SP1 HF1, the fileservice.log contains several errors referring to MemoryMappedFiles as shown below.
INFO Accelrys.FileService.Logger [(null)] - The stream 'Global\\02333bdb-6383-43fe-9d44-04c9d7da01e3' was not read after 10 minutes, so it will be destroyed.
ERROR Accelrys.FileService.Logger [(null)] - Unexpected exception caught while deleting stream 'Global\\02333bdb-6383-43fe-9d44-04c9d7da01e3'.
System.IO.FileNotFoundException: Unable to find the specified file.
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.MemoryMappedFiles.MemoryMappedFile.OpenCore(String mapName, HandleInheritability inheritability, Int32 desiredAccessRights, Boolean createOrOpen)
at System.IO.MemoryMappedFiles.MemoryMappedFile.OpenExisting(String mapName, MemoryMappedFileRights desiredAccessRights, HandleInheritability inheritability)
at Accelrys.FileService.RestApi.Controllers.StreamsController.<>c__DisplayClass2.b__1()

As per Workbook R & D, MemoryMapped file goes out of scope and gets disposed before it is explicitly disposed by the system causing the above errors. There is a defect NBK-33972 entered for this issue in BIOVIA Jira system. This issue is fixed in the BIOVIA Workbook 2023 code so that MemoryMapped file will not be disposed before we explicitly dispose it.