ISO 8571-3:1988/Amd 2:1993 PDF

Overview - ISO 8571-3:1988/Amd.2:1993 (Overlapped access)

ISO 8571-3:1988/Amd.2:1993 is an amendment to the OSI File Transfer, Access and Management (FTAM) File Service Definition that extends the externally visible file service to support overlapped access. Its objective is to improve efficiency when a single initiator performs many read and update operations on structured files by allowing multiple bulk data transfers to be overlapped rather than strictly serialized.

Key topics and technical requirements

• Overlapped access modes: Defines two degrees of overlap:
  • Consecutive access - allows queuing of future read/write requests while earlier BDT (bulk data transfer) actions are in progress; transfers are effectively serialized but requested ahead of time.
  • Concurrent access - allows parallel execution of read and write transfers so read and write operations can be interleaved and processed when resources free up.
• Concurrency control and serializability: Ensures that the net effect on the virtual filestore remains serializable (i.e., equivalent to some serial ordering of requests) even when concurrent transfers introduce non-determinism.
• Functional units added:
  • Consecutive access functional unit
  • Concurrent access functional unit
  • Related mechanisms: FADU (File Access Data Unit) locking, grouping, transfer restart and recovery
• Primitives and parameters: Introduces or conditions parameters used by the internal file service when overlapped access is negotiated, including:
  • Bulk transfer number and transfer number (identify particular bulk transfers)
  • Transfer window (limits number of uncompleted bulk transfers)
  • Degree of overlap (negotiated at file open)
  • Last transfer end request/response indicators, concurrent recovery point
• Bulk data transfer services: Reiterates read/write/data-end/cancel services and adds checkpointing/restarting behavior for overlapped transfers. The amendment keeps the design rule of one file selection per association and one file open per selection.

Practical applications

• Improves throughput and reduces control overhead for applications performing many small or frequent read/write operations on structured files.
• Useful for networked file systems, remote database/file access, and bulk data ingestion or streaming where parallelizing transfers reduces latency.
• Supports robust recovery and restart semantics for interrupted multi-transfer operations.

Who should use this standard

• Protocol designers and implementers of FTAM and OSI-based file services
• Vendors of enterprise file servers, storage gateways, and networked filesystem products
• System integrators building high-throughput remote file access or structured file update solutions
• Standards and compliance teams validating FTAM implementations

Related standards

• ISO 8571 series (Part 1: general, Part 2: Virtual Filestore, Part 4: Protocol Specification, Part 5: PICS proforma, Part 7: General introduction)
• Developed under ISO/IEC JTC 1 (Information technology)

Keywords: ISO 8571-3, overlapped access, FTAM, Open Systems Interconnection, bulk data transfer, consecutive access, concurrent access, transfer window, FADU locking, file service definition.