Z39.50 is a client-server protocol enabling libraries to search remote catalogs and retrieve bibliographic records. For Koha users, Z39.50 is essential for copy cataloging, dramatically reducing the time required to add materials to your collection by importing existing MARC records from major libraries and databases.

What is Z39.50?

Developed by the Library of Congress and standardized as ANSI/NISO Z39.50 and ISO 23950, this protocol defines how library systems communicate to:

  • Search Remote Catalogs - Query thousands of libraries simultaneously
  • Retrieve MARC Records - Download complete bibliographic data
  • Copy Cataloging - Import records instead of creating from scratch
  • Authority Control - Access authority records from authoritative sources
  • Interlibrary Loan - Support resource sharing workflows

Z39.50 acts as a universal translator, allowing Koha to communicate with any compliant library system regardless of vendor or database structure.

How Z39.50 Works

The Z39.50 Architecture

┌──────────────┐                    ┌──────────────┐
│              │   Z39.50 Query     │              │
│    CLIENT    │ ─────────────────> │    SERVER    │
│   (Koha)     │                    │   (LC/OCLC)  │
│              │ <───────────────── │              │
└──────────────┘   MARC Records     └──────────────┘

The Process

  1. Connection: Client (Koha) connects to a Z39.50 server (e.g., Library of Congress)
  2. Query: Client sends a search query (e.g., ISBN: 9780123456789)
  3. Search: Server searches its database using local indexing
  4. Response: Server returns matching records in MARC format
  5. Import: Client displays results; cataloger selects records to import
  6. Download: Selected MARC records transfer to the client system

Search Attributes

Z39.50 supports various search points:

  • ISBN/ISSN - Most precise for copy cataloging
  • Title - Keyword or phrase searches
  • Author - Personal or corporate names
  • Subject - Topical searches
  • LCCN - Library of Congress Control Number
  • Standard Number - Other identifiers
  • Any - Searches all fields

Why Z39.50 Matters for Libraries

1. Copy Cataloging

Instead of creating original MARC records from scratch, catalogers can:

  • Search the Library of Congress catalog by ISBN
  • Download high-quality, authoritative records
  • Edit downloaded records to fit local needs
  • Save hours per record compared to original cataloging

2. Quality Control

Records from authoritative sources like LC are:

  • Created by expert catalogers following RDA standards
  • Reviewed for accuracy and completeness
  • Linked to authority records
  • Updated when standards change

3. Consistency

Using records from shared sources ensures:

  • Standardized subject headings
  • Authorized name forms
  • Correct classification numbers
  • Uniform bibliographic practices

4. Resource Sharing

Z39.50 enables:

  • Union catalog searching - Search multiple libraries at once
  • Interlibrary loan - Locate items and verify holdings
  • Consortial resource sharing - Pool collections across institutions

5. Cost Savings

By importing existing records rather than creating originals:

  • Reduce cataloging time by 70-90%
  • Minimize staffing requirements
  • Lower training costs
  • Decrease errors and rework

Z39.50 in Koha

Koha includes a powerful Z39.50 client that allows catalogers to search multiple targets simultaneously.

Configuring Z39.50 in Koha

Administration → Z39.50/SRU servers

For each target, configure:

  • Server name - Descriptive label
  • Hostname - Server address
  • Port - Usually 210 or 7090
  • Database name - Server-specific identifier
  • User/Password - If required
  • Syntax - MARC21, UNIMARC, etc.
  • Encoding - MARC-8 or UTF-8

Using Z39.50 for Cataloging

From Cataloging → New from Z39.50:

  1. Enter search terms (ISBN recommended for best results)
  2. Select which servers to query
  3. Click Search
  4. Review results from all targets
  5. Preview MARC records
  6. Import selected record into Koha
  7. Edit as needed and save

See our comprehensive Z39.50 Server Directory for connection details, including:

  • Library of Congress - Largest source of authoritative records
  • OCLC WorldCat - Over 500 million bibliographic records
  • British Library - UK national library
  • National Libraries - Canada, Australia, Germany, France, etc.
  • Academic Consortia - OCLC members, university networks
  • Public Library Networks - State and regional catalogs

Z39.50 vs. SRU

SRU (Search/Retrieve via URL) is a more modern alternative to Z39.50:

Feature Z39.50 SRU
Protocol Binary Web-based (HTTP/XML)
Year Created 1988 2004
Complexity High Lower
Firewall-Friendly No Yes
Browser-Accessible No Yes
Support in Koha Excellent Good

Koha supports both protocols. Many servers now offer both Z39.50 and SRU access. SRU is gradually replacing Z39.50 for new implementations, but Z39.50 remains widely used.

Common Z39.50 Issues and Solutions

Connection Failures

  • Cause: Firewall blocking port 210
  • Solution: Work with IT to allow outbound Z39.50 traffic

No Results

  • Cause: Incorrect database name or search syntax
  • Solution: Verify server settings; try different search types

Slow Response

  • Cause: Network latency or server load
  • Solution: Query fewer targets simultaneously; use faster servers

Encoding Errors

  • Cause: Character set mismatch (MARC-8 vs UTF-8)
  • Solution: Configure proper encoding in server settings

Duplicate Records

  • Cause: Importing multiple versions of same record
  • Solution: Search existing catalog first; use duplicate detection

Best Practices for Z39.50 in Koha

  1. Search by ISBN First - Most accurate and fastest results
  2. Use Authoritative Sources - LC, national libraries, OCLC
  3. Configure Multiple Targets - Fallback options if one fails
  4. Test Regularly - Server settings and access change
  5. Document Settings - Keep a list of working configurations
  6. Train Staff - Show catalogers how to evaluate record quality
  7. Review Imported Records - Don’t accept blindly; edit for local needs

Z39.50 Alternatives and Complements

OCLC Connexion

Web-based cataloging interface for OCLC members with enhanced features beyond basic Z39.50.

MarcEdit

Desktop tool for batch MARC editing and Z39.50 harvesting.

Vendor Record Services

Many book vendors provide MARC records with purchased materials, reducing need for Z39.50 searches.

Linked Data

Future catalogs may use APIs and linked data rather than Z39.50, but migration will take years.

Z39.50 Resources

Conclusion

Z39.50 has been the backbone of library resource sharing for over 30 years. Despite its age and complexity, it remains essential for copy cataloging and interlibrary loan. Koha’s robust Z39.50 client makes it easy to leverage this protocol to improve cataloging efficiency and access authoritative bibliographic records.

As libraries transition to newer technologies like SRU and linked data APIs, Z39.50 will gradually decline. But for the foreseeable future, understanding and using Z39.50 effectively is a core competency for library staff working with integrated library systems.

Need help configuring Z39.50 servers in Koha? Our team provides setup, training, and troubleshooting support. Contact us to learn more.