LC Folio Z39.50/SRW/SRU Server Configuration Guidelines

LC Z39.50/SRW/SRU Server Configuration Guidelines

This document provides the detailed technical information for Z39.50 and SRU client developers and implementors necessary to access and interwork with the LC Folio Z39.50 Server. This document assumes a general familiarity with Z39.50 and SRU.

The LC Folio Z39.50 Server conforms to Z39.50-1995 (Version 3) of the standard. A subset of attributes from the bib-1 attribute set are supported, and codes from the bib-1 diagnostic set are utilized.

LC has implemented IndexData's MetaProxy, which functions as an SRW/SRU/Z39.50 gateway to LC's various Folio and Zebra Z39.50 servers. The SRW and SRU Web services conform to version 1.1 of the standard.

When connecting to Library of Congress catalogs using Z39.50, we recommend using the DNS hostname rather than a static IP address to ensure continued access when IP addresses change.

Please note: In July 2015, the Library updated its Z39.50 Metaproxy server. This process resulted in deprecation of the static IP originally associated with the lx2.loc.gov DSN name. After September 28, 2015, institutions using this deprecated static IP (140.147.249.67) will no longer be able to access LC catalog metadata unless they modify the Z39.50 target information in their applications.

Please note: In July 2025, the Library changed the catalog from Voyager to Folio. None of the connection details have changed, but the attributes supported are significantly reduced.

Please send questions to the Network Development and MARC Standards Office at [email protected]

Z39.50 Services Supported
SRW/SRU Services Supported
Internet Addresses, Databases, and Hours of Availability
Initialization Service (Z39.50)
Search Service
Present Service (Z39.50)
XML Schemas Supported (SRW/SRU)
Queries Supported (SRW/SRU)
Use Attributes Supported (Z39.50)
Relation Attributes Supported (Z39.50)
Position Attributes Supported (Z39.50)
Structure Attributes Supported (Z39.50)
Truncation Attributes Supported (Z39.50)
Completeness Attributes Supported (Z39.50)
Required and Default Attributes (Z39.50)
Search Term Processing in LC System
Limitations of Folio Server

Z39.50 Services Supported

The LC server supports the following services:

Initialization
Search
Present

SRW/SRU Services Supported

The LC SRW/SRU server supports the following services:

Explain
searchRetrieve

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Internet Addresses, Databases, and Hours of Availability

Library of Congress Catalog

    Domain name:    lx2.loc.gov
    Port:           210
    Database name:  LCDB           (UTF-8 records)    
    Database name:  LCDB_MARC8     (MARC8 records)    
    Database name:  NLSBPH         (UTF-8 records)    
    Availability:   24 hours/day; 7 days/week
    Z39.50 Explain record:   LC Catalog Z39.50 Explain Record
    SRU Base URL (http):  http://lx2.loc.gov:210/lcdb?
    SRU Base URL (https): https://lx2.loc.gov/sru/lcdb?
    SRU Explain record:  LC Catalog SRU Explain Record

National Library Service for the Blind and Print Disabled Union Catalog

    Domain name:    lx2.loc.gov
    Port:           210
    Database name:  NLSBPH         (UTF-8 records)
    Database name:  NLSBPH_MARC8   (MARC-8 records)
    Availability:   24 hours/day; 7 days/week
    Z39.50 Explain record:  NLS/BPH Explain Record
    SRU Base URL (http):  http://lx2.loc.gov:210/nslbph?
    SRU Base URL (https): https://lx2.loc.gov/sru/nlsbph?
    SRU Explain record:  NLSBPH SRU Explain Record

Name Authority File

    Domain name:    lx2.loc.gov
    Port:           210
    Database name:  NAF           (UTF-8 records)
    Availability:   24 hours/day; 7 days/week
    SRU Base URL (http):  http://lx2.loc.gov:210/naf?
    SRU Base URL (https): https://lx2.loc.gov/sru/naf?
    SRU Explain record:  NAF SRU Explain Record

Subject Authority File

    Domain name:    lx2.loc.gov
    Port:           210
    Database name:  SAF          (UTF-8 records)
    Availability:   24 hours/day; 7 days/week
    SRU Base URL (http):  http://lx2.loc.gov:210/saf?
    SRU Base URL (https): https://lx2.loc.gov/sru/saf?
    SRU Explain record:  SAF SRU Explain Record

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Initialization Service (Z39.50)

Protocol Version
    Z39.50-1995 (Version 3)

Options Supported
    Search
    Present

Preferred Message Size
    LC will negotiate Client down to 32,768 bytes if requested size exceeds 32,768 bytes, and accept
    Client proposal if it is less than 32,768 bytes.

Maximum Record Size
    Server will accept Client proposal

ID Authentication
    User-id and password are not required by LC Server

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Search Service

Result Set Name
    Only "default" is supported (case insensitive)

Database Names
    "LCDB"         Library of Congress Bibliographic Database (UTF-8)
    "LCDB_MARC8"   Library of Congress Bibliographic Database (MARC-8)
  
    "NLSBPH"       National Library Service for the Blind and Print Disabled (UTF-8)
    "NLSBPH_MARC8" National Library Service for the Blind and Print Disabled (MARC-8)
    "AllVoyager"   LCDB (UTF-8 only)
    "NAF"          Name Authority File (UTF-8 only)
    "SAF"          Subject Authority File (UTF-8 only)

Query
    Type-1 only is supported

Attribute Set ID
    Bib-1 only is supported

Operand
    The Result Set ID (i.e., "default") cannot be used in the Operand.
    Qualifying searches are not supported

Operators Supported:
    AND
    OR
    AND-NOT

Result Set Maximum is 10,000 records

Session Inactivity Timer
    60 seconds

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Present Service (Z39.50)

Record Syntaxes Supported
    MARC 21  (OID = 1.2.840.10003.5.10)    
    XML   (OID = 1.2.840.10003.5.109.10)

Element Set Names Supported
    Bibliographic Databases
    "F"  --  Full (MARC records)
    "dc"  --  Dublin Core (XML records)
    "mods"  -- MODS (XML records)
    "marcxml" -- MARCXML (XML records), default schema for XML    

    Authority Databases
    "F" --  Full MARC records
    "marcxml" -- MARCXML (XML records), default schema for XML
    "mads" -- MADS (XML records)
	

Present Response Maximum is 50 records

XML Schemas Supported (SRW/SRU)

"dc" -- Dublin Core (bibliographic records)
"mads" -- MADS (authority records)
"mods" -- MODS (bibliographic records)
"marcxml" -- MARCXML - the default schema
"bibframe2" BIBFRAME RDF (XML descriptions)
"bibframe2a" BIBFRAME with authority URIs

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Queries Supported (SRU)

Bibliographic Databases (LCDB)

CQL Index
	cql.anywhere

Dublin Core Index
	dc.author
	dc.creator    
	dc.publisher    
	dc.subject
	dc.title

Bath Index
    
	bath.name
	bath.personalName
	bath.conferenceName
	bath.corporateName
	bath.geographicName
	bath.isbn
	bath.issn
	bath.lccn  
	bath.standardIdentifier
	bath.publisher

Name Authority File (NAF)

CQL Index
    cql.anywhere

Dublin Core Index
    dc.title

Bath Index
        
    bath.name
    bath.personalName
    bath.conferenceName
    bath.corporateName
    bath.geographicName
    bath.uniformTitle
    bath.isbn
    bath.issn    
    bath.lccn    
    bath.standardIdentifier
    

Local Index
    
    local.id (Local Control number)    
    local.primaryHeading

Subject Authority File (SAF)

CQL Index
    cql.anywhere

Dublin Core Index
    dc.title

Bath Index
        
    bath.name
    bath.personalName
    bath.conferenceName
    bath.corporateName
    bath.uniformTitle
    bath.geographicName    
    bath.lccn
    bath.standardIdentifier


Local Index
    local.id (Local Control number)    
    local.primaryHeading

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Use Attributes Supported (Z39.50):

Bibliographic Databases (LCDB)

   
      Value   Description
      -----   -------------------------
        1     Personal name
        2     Corporate name
        3     Conference name
        4     Title        
        7     ISBN
        8     ISSN
        9     LCCN	   
       16     LC Call Number 	   
       21     Subject heading
     1003     Author
     1007     Standard Idnetifier
     1016     Any (keyword)
     1211     OCLC Number

Name Authority File (NAF)

      Value   Description
      -----   -------------------------
        1     Personal name
        2     Corporate name
        3     Conference name
        4     Title
        6     Uniform title        
        9     LCCN (010)       
     1002     Name
     1007     Standard identifier   
     1016     Any (keyword)     
     5009     Record ID (001)

Subject Authority File (SAF)

      Value   Description
      -----   -------------------------
        4     Title
       21     Subject heading
       47     Subject subdivision
     1002     Name
     1007     Standard identifier
     1009     Subject Personal Name     
     1016     Any (keyword)
     1073     Subject-name conference
     1074     Subject-name corporate
     1075     Subject-genre/form
     1076     Subject-name geographical
     1079     Subject topical
     5075     Subject subdivision form
     5076     Subject subdivision geographical
     5077     Subject subdivision chronological
     5079     Subject subdivision general

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Relation Attributes Supported (Z39.50):

      Value   Description
      -----   ---------------
        3     Equal

        Values other than "3" are accepted, but not regarded.

Position Attributes Supported (Z39.50):

      Value   Description
      -----   ---------------
        1     First in field
        3     Any

Structure Attributes Supported (Z39.50):

      Value   Description
      -----   ---------------
        1     Phrase

        Values other than "1" are accepted, but not regarded.

Truncation Attributes Supported (Z39.50):

      Value   Description
      -----   ---------------
        1     Right truncation
      100     Do not truncate

Completeness Attributes Supported (Z39.50):

      Value  Description
      -----  --------------------
        1    Incomplete subfield

        Values other than "1" are accepted, but not regarded.

Required and Default Attributes

      Requirements and Defaults:   The Use attribute is REQUIRED.

      For the other attributes, if an attribute type and value are not supplied by the
      client, the following defaults are applied at LC:

            RELATION:     --  Equal (value=3)
            POSITION:     --  Any   (value=3)
            STRUCTURE:    --  Phrase (value=1)
            TRUNCATION:   --  Do not truncate  (value=100)
            COMPLETENESS: --  Incomplete subfield (value=1)

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Search Term Processing in LC System

Keyword searches (i.e., Position attribute = "any-position-in-field"):

Keyword search terms can appear anywhere in the field.
If multiple words appear in the same search term, the search term will be processed as a phrase (ordered, adjacent word list).
If the words appear in separate operands (ANDed together) they can appear in different fields in the same record.
Name keywords: A keyword search term can be the first, middle, or last name. If more than one name appears in a keyword search term, the order is significant. A personal last name should precede first name.
Keyword indexing does not include phrases that cross subfield boundaries. If the search term contains a phrase that may cross subfield boundaries (e.g., subject heading, LC call number, etc.), use a left-anchored (right-truncated) search. In other words, Position attribute = "first-in-field"; Truncation attribute = "right truncation".

Phrase searches (i.e., multiple-word search terms):

Phrase search terms can appear anywhere in the field.
Phrase searches that include the "First-in-field" Position attribute should begin with the first significant word in the field.
Boolean operators cannot be used with phrase searches that include the "First-in-field" Position attribute.
Name phrase searches: The order in which the names appear in the search term is significant. In other words, the surname should appear first (with or without comma) in order to match against entry fields in LC indexes.

Number searches (ISBN, ISSN, LCCN, etc.):

Use a hyphen in all ISSN search terms (e.g., 1234-5678).
Do not include hyphens in ISBN or LCCN search terms.
LCCN search terms should be in normalized format (i.e., include any prefix, spaces, or zero fill). For example, LCCN 91-13 should be "91000013" in the search term.

Qualifying Searches: Searches are not supported against previous result sets.

Wild Card/Truncation: The questions mark ("?") is supported as a truncation character.

Sort Order: Records are sorted by the contents of the MARC 245 field.

Limitations of Folio Server

There is a limit of 10,000 records that can be retrieved in a result set.
When the Folio server result set is a medium or a small set (based on the size of result set in relation to large-set, small-set, and medium-set number parameters in the Search Request), the following three encoding problems can result:

When records are expected in the Search Response (e.g., a medium set or a small set), the presentStatus is a "0" (success) instead of a "5" (failure).
When a non-surrogate diagnostic record is returned instead of result set records in the Search Response, the value of numberOfRecordsReturned is "0" instead of "1".
The non-surrogate diagnostic record never contains an addInfo (which is mandatory in the standard).

If these problems make working with the Folio server difficult, we suggest that the client small-set and medium-set number be set to zero and the large-set to one (making every set a large set).

Last update: 2026-01-23

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