Overview
ISO/IEC 9316-2:2000 specifies the Common Access Method (CAM) for Small Computer System Interface-2 (SCSI-2). The standard defines a consistent transport and SCSI interface module so multiple environments can adopt a common procedure for supporting SCSI devices. CAM provides a structured method to coordinate software (device drivers, target/peripheral drivers) and hardware (host bus adapters - HBAs) for SCSI I/O and control.
Key topics and technical requirements
- CAM architecture: roles and interactions of XPT (transport), SIM (SCSI interface module), and peripheral/target drivers.
- CAM control blocks (CCBs): standardized CCB header fields, function codes, CAM status values and how to use CCBs to request I/O and control SCSI behavior.
- SCSI I/O and target services: execute SCSI I/O, command linking, host target mode, phase-cognizant mode, IMMEDIATE NOTIFY / NOTIFY ACKNOWLEDGE operations.
- Queueing & tagging: SIM queuing, tagged queue actions and SCSI request queues for logical units.
- Error handling & recovery: SCSI resets, aborts, terminate I/O processes, autosense and residual reporting.
- Asynchronous events & callbacks: registration and handling of asynchronous callbacks for events reported by SIM or HBA.
- OS-dependent mapping: guidance and examples for OSD (operating system dependent) environments (sample environments include UNIVOS, LANOS, DOS) covering initialization, pointer mapping and callbacks.
- HBA engines and inquiry: HBA engine model, engine inquiry and execute-engine request interfaces.
- Data transfer support: scatter/gather list descriptions, data buffer pointers and transfer length handling.
Practical applications and users
This standard is intended for:
- Device driver and OS developers building SCSI peripheral and target drivers implementing a portable, OS-independent interface.
- HBA and storage controller vendors implementing SIM and engine interfaces so their hardware interoperates across multiple OS environments.
- Storage integrators and system architects needing a consistent SCSI transport layer for multi-platform deployments.
- Test and QA teams validating SCSI command handling, queueing, error recovery and target/initiator behavior.
Adopting ISO/IEC 9316-2:2000 enables consistent SCSI-2 support across software and hardware, reduces platform-specific driver work, and improves interoperability of HBAs and storage devices.
Related standards (brief)
- Other SCSI and SCSI-2 family standards and vendor HBA specifications complement CAM. Implementers should consult the SCSI-2 core documents and HBA vendor guides for low-level electrical and protocol details.
Open preview (PDF)Information technology — Small computer system interface-2 (SCSI-2) — Part 2: Common Access Method (CAM) Transport and SCSI interface module
