• Java 11 is required
  • Tomcat 8 (servlet 3.1)
  • On the command line when starting up Tomcat/TDS, you must specify -Dtds.content.root.path=<content root> where <content root> points to the top of the content directory. Note that this is ${tomcat_home}/content/, not${tomcat_home}/content/thredds/. Don’t forget the trailing slash. For example:



The configuration catalogs and internal state of the TDS has been extensively re-worked to be able to scale to large numbers of catalogs, datasets, and internal objects without excessive use of memory. A running TDS can be triggered to reread the configuration catalogs without having to restart. It can be configured to reread only changed catalogs, for fast incremental updates. Other features have been added to make writing configuration catalogs more maintainable, including the <catalogScan> element, and default and standard services.

The other major enhancement is that GridDataset is replaced by FeatureDatasetCoverage, to better support very large feature collections. The Coverage API works with coordinate values (not array indices), which solves various intractable problems that arise when using array index subsetting on large collections.

A number of API enhancements have been made to take advantage of evolution in the Java language, for example try-with-resource and foreach constructs. The use of these make code simpler and more reliable.

Deprecated classes and methods have been removed, and the module structure and third-party jar use has been improved.

TDS Data Services

Netcdf Subset Service (NCSS)

NCSS queries and responses have been improved and clarified. Generally the previous queries are backwards compatible. See NCSS Reference for details.

New functionality:

  • 2D time can now be handled for gridded datasets, with addition of runtime and timeOffset parameters.
  • Handling of interval coordinates has been clarified.
  • Use ensCoord to select an ensemble member.

Minor syntax changes:

  • Use time=all instead of temporal=all
  • For station datasets, subset=stns or subset=bb is not needed. Just define stns or a bounding box.


You no longer turn catalog caching on or off, but you can control how many catalogs are cached (see here for the new syntax).

The following is no longer used:

  • By default, most services are enabled, but may still be turned off in threddsConfig.xml.

Java Web Start

Java Web Start has been deprecated as of Java 9, and has been removed in Java 11, which is the Long-term Release post-Java 8. Due to these changes, the netCDF-Java project no longer provide Java Web Start files as of version 5.0. Following suite, the TDS no longer provide any Web Start based Viewers on Dataset pages out of the box.


Catalog Schema Changes

Schema version is now 1.2.

Client Catalogs

  • <service> elements may not be nested inside of <dataset> elements, they must be directly contained in the <catalog> element.

Server Configuration Catalogs

  • The <catalogScan> element is now available, which scans a directory for catalog files (any file ending in xml)
  • The <datasetFmrc> element is no longer supported
  • <datasetRoot> elements may not be contained inside of service elements, they must be directly contained in the <catalog> element
  • <service> elements may not be nested inside of <dataset> elements, they must be directly contained in the <catalog> element.
  • <service> elements no longer need to be explicitly defined in each config catalog, but may reference user defined global services
  • If the datatype/featureType is defined for a dataset, then the <service> element may be omitted, and the default set of services for that datatype will be used.
  • The expires attribute is no longer used.


  • thredds.servlet.Viewer has InvDatasetImpl changed to Dataset
  • thredds.servlet.ViewerLinkProvider has InvDatasetImpl changed to Dataset
  • thredds.server.viewer.dataservice.ViewerService has InvDatasetImpl changed to Dataset


  • addID is no longer needed, ids are always added
  • addDatasetSize is no longer needed, the dataset size is always added
  • With addLatest, the service name is no longer used, it is always Resolver, and the correct service is automatically added. Use addLatest attribute for simple case.
  • fileSort: by default, datasets at each collection level are listed in increasing order by filename. To change to decreasing order, use the fileSort element.
  • sort: deprecated in favor of filesSort
  • User pluggable classes implementing UserImplType (crawlableDatasetImpl, crawlableDatasetFilterImpl, crawlableDatasetLabelerImpl, crawlableDatasetSorterImpl) are no longer supported. (This was never officially released or documented).
  • DatasetScan details are here

Standard Services

  • The TDS provides standard service elements, which know which services are appropriate for each Feature Type.
  • User defined services in the root catalog are global and can be referenced by name in any other config catalog.
  • User defined services in non-root catalogs are local to that catalog and override (by name) any global services.
  • All services are enabled unless explicitly disabled. ** Except for remote catalog services.
  • Standard service details are here)

Feature Collections

  • The update element default is now startup="never", meaning do not update collection on start up, and use existing indices when the collection is accessed.
  • The fileSort element is now inside the featureCollection itself, so it can be processed uniformly for all types of feature collections. When a collection shows a list of files, the files will be sorted by increasing name. To use a decreasing sort, use the element <filesSort increasing="false" /> inside the featureCollection element. This supersedes the old way of placing that element in the <gribConfig> element, or the older verbose lexigraphicByName element:

        <lexigraphicByName increasing="false" />  // deprecated
  • Feature Collection details are here

Recommendations for 5.x catalogs

  • Put all <datasetRoot> elements in root catalog.
  • Put all <catalogScan> elements in root catalog.
  • Use StandardServices when possible. Annotate your datasets with featureType / dataType.
  • Put all user-defined <service> elements in root catalog.
  • Only use user-defined <service> elements in non-root catalogs when they are experimental or truly a special case.

Recommendations for ESGF

You must determine the number of datasets that are contained in all of your catalogs. To get a report, enable Remote Management, and from https://server/thredds/admin/debug, select “Make Catalog Report”. This may take 5-20 minutes, depending on the numbers of catalogs.

Add the <ConfigCatalog> element to threddsConfig.xml:



  • keepInMemory: using the default value of 100 is probably good enough.
  • reread: use value of check to only read changed catalogs when restarting TDS.
  • dir is where the catalog cache files are kept. Use the default directory (or symlink to another place) unless you have a good reason to change.
  • maxDatasets: this is the number you found in step 1. Typical values for ESGF are 1 - 7 million. This is a maximum, so it’s ok to make it bigger than you need.

Here are some additional, optional changes you can make to increase maintainability:

  1. Place all datasetRoot elements in the top catalog
  2. Place all service elements in the root catalog (catalog.xml). These can be referenced from any catalog.
  3. Remove <service> elements from non-root catalogs.
  4. Add a catalogScan element to the root catalog, replacing the list of catalogRefs listing all the other catalogs.
    • This assumes that other catalogs live in a subdirectory under the root, for example ${tds.content.root.path}/thredds/esgcet/**.

For example:

  <?xml version='1.0' encoding='UTF-8'?>
  <catalog name="ESGF Master Catalog" version="1.2"
        xmlns:xsi="" xmlns:xlink=""

    <datasetRoot location="/esg/data" path="esg_testroot"/>
    <datasetRoot location="/esg/arc/data/" path="esg_obs4MIPs"/>
    <datasetRoot location="/esg/cordex/data/" path="esg_cordex"/>
    <datasetRoot location="/esg/specs/data/" path="esg_specs"/>

    <service base="/thredds/dodsC/" desc="OpenDAP" name="gridded" serviceType="OpenDAP">
      <property name="requires_authorization" value="false"/>
      <property name="application" value="Web Browser"/>

    <service base="" name="fileservice" serviceType="Compound">
      <service base="/thredds/fileServer/" desc="HTTPServer" name="HTTPServer" serviceType="HTTPServer">
        <property name="requires_authorization" value="true"/>
        <property name="application" value="Web Browser"/>
        <property name="application" value="Web Script"/>

      <service base="gsi" desc="GridFTP" name="GridFTPServer" serviceType="GridFTP">
        <property name="requires_authorization" value="true"/>
        <property name="application" value="DataMover-Lite"/>

      <service base="/thredds/dodsC/" desc="OpenDAP" name="OpenDAPFiles" serviceType="OpenDAP">
        <property name="requires_authorization" value="false"/>
        <property name="application" value="Web Browser"/>

    <catalogScan name="ESGF catalogs" path="esgcet" location="esgcet" />