Systematic approach to identifying underlying issues in processes systems and operations

IMS DB

IMS Database

Enhanced Definition

The database component of IMS using a hierarchical data model for organizing information. IMS DB represents data as tree structures with parent-child relationships.

- Hierarchical (tree) data structure
- Segment-based organization
- Fast path for high performance
- Multiple access paths
- Logical relationships
Database Structure:
- Root Segment: Top of hierarchy
- Child Segments: Dependent segments
- Twin Segments: Multiple occurrences at same level
- Segment Types: Different data record types
- Database Records: Complete hierarchical instances
Access Methods:
- Sequential Processing: Navigate hierarchy
- Direct Access: Via keys or secondary indexes
- Path Calls: Retrieve multiple segments
- Boolean operators: Complex selection
- Secondary Indexing: Alternate access paths
Database Types:
- Full Function: Complete database features
- Fast Path: Ultra-high performance, limited features
- DEDBs (Data Entry Databases): Online updates
- MSDBs (Main Storage Databases): Memory-resident
DL/I (Data Language/I):
- IMS database programming interface
- Call-level interface from COBOL, PL/I, etc.
- Function codes (GU, GN, GHU, GHN, REPL, DLET, ISRT)
- Segment Search Arguments (SSAs)
- PCB (Program Communication Block)