JA Technology Solutions
COBOL Copybook Explorer
Explore COBOL copybook structures with interactive tree view, field layout, SQL conversion, JSON Schema generation, sample data decoding, and visual hex ruler.
COBOL Copybook Explorer
Paste or upload a COBOL copybook and explore the record structure across four views: a collapsible hierarchy tree showing levels, PIC clauses, offsets, and byte lengths at every node; a flat field layout with start/end positions, lengths, data types, and REDEFINES relationships (CSV or Excel export); SQL CREATE TABLE generation in 5 dialects and JSON Schema for API design; and a sample-data decoder that renders raw records as readable values (ASCII, packed decimal, binary, zoned decimal). A full-length visual hex ruler lines up every field against the raw bytes. Handles PIC clauses, COMP-3, COMP/BINARY, REDEFINES, OCCURS, group items, and level 88 conditions. Everything runs in your browser — your copybooks and sample data never leave your machine.
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What Is a COBOL Copybook?
A COBOL copybook is a source file containing data structure definitions that are included (copied) into COBOL programs using the COPY statement. Copybooks define the record layout for files, database tables, communication areas, and working storage — specifying field names, level numbers, PIC (picture) clauses, and USAGE declarations. A PIC clause like PIC S9(7)V99 COMP-3 defines a signed 7-digit number with 2 implied decimal places stored in packed decimal format. Copybooks are the Rosetta Stone for mainframe data — without them, binary data files are undecipherable.
Why Copybook Analysis Matters
Every data extraction, migration, or integration project involving mainframe or IBM i COBOL systems starts with the copybook. It tells you exactly where each field starts, how long it is, what type it is (text, packed decimal, binary, zoned decimal), and how many decimal places numeric fields carry. This tool parses copybooks into a visual layout with byte offsets, handles REDEFINES (multiple interpretations of the same bytes), OCCURS (arrays), group items (nested structures), and level 88 conditions (value-based flags). The SQL conversion feature generates CREATE TABLE statements in five dialects, mapping COBOL types to appropriate SQL column types.
Mainframe Data Migration
Copybook analysis is the foundation of any mainframe data migration. I use copybook definitions to build extraction pipelines that correctly decode every field type — text, packed decimal, binary, zoned decimal — and deliver clean, validated data to modern target systems. Whether you are migrating from a mainframe to cloud, extracting data for a data warehouse, or building real-time integration between mainframe and modern applications, learn about migration services, explore ETL development and IBM i services, or get in touch.
All tools run entirely in your browser. Your data never leaves your machine. Need help? Ask James.