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BSAM

Basic Sequential Access Method

Enhanced Definition

A low-level access method for reading and writing sequential datasets that provides direct programmer control over I/O operations, buffering, and error handling. BSAM offers more flexibility than QSAM but requires more detailed programming.

Key Characteristics

- Block-level I/O control
- Programmer-managed buffering
- Synchronous and asynchronous I/O support
- Greater control over I/O timing and sequencing
- More complex programming than QSAM
BSAM Operations:
- READ: Retrieve data blocks from input
- WRITE: Output data blocks to datasets
- CHECK: Verify completion of asynchronous I/O
- POINT: Position to specific dataset location
- CLOSE: Terminate dataset processing
Buffer Management:
- Programmer allocates and manages buffers
- Multiple buffer support for overlapped I/O
- Explicit WAIT for I/O completion
- Control over buffer size and quantity
- Optimization opportunities for specific patterns
When to Use BSAM:
- Need precise control over I/O timing
- Implementing specialized access patterns
- Optimizing for specific performance requirements
- Processing variable-length spanned records
- Interfacing with low-level system functions

Use Cases

- High-performance data transformation utilities
- Specialized file processing applications
- System programming and utility development
- Legacy application maintenance
- Performance-critical batch processing