How to open .XDD files on Windows
To open .XDD files on Windows, determine the source of the file: if it came from FairCom RTG utilities or COBOL-IT projects, treat it as an RTG/COBOL data dictionary; otherwise it may belong to another program (e.g., Xfit).
Step-by-step instructions
- Determine the source of the file: if it came from FairCom RTG utilities or COBOL-IT projects, treat it as an RTG/COBOL data dictionary; otherwise it may belong to another program (e.g., Xfit).
- If it is an RTG XDD file, open it in an XML-capable text editor to view the <schema> / <key> structure, or open/import it in the relevant FairCom RTG utility or COBOL-IT tooling that references “settings from an XDD file”.
- If it does not resemble XML, use the originating application/workflow (for example, Xfit if that is the known source).
Common issues
The .xdd file opens as unreadable characters (not XML)
Many .xdd files are RTG XDD schemas stored as XML, but the extension is also used by other niche software. If the content is not XML, it may not be a FairCom RTG XDD schema.
- Open the file in a text editor and check whether it starts with XML-like content and includes elements such as <schema> or <key> (typical of FairCom RTG XDD).
- If it is not XML, identify the source application/workflow (file-extensions.org notes Xfit usage) and open it with that application instead.
Your tool cannot interpret the data file correctly even with the .xdd present
In RTG/COBOL workflows, the XDD must match the actual record layout (COBOL FD definitions) and index definitions. A mismatched or outdated XDD can cause wrong field interpretation.
- Regenerate the XDD from the authoritative source definitions (e.g., COBOL FDs) using the appropriate generator workflow (COBOL-IT docs describe -fgen-xdd; FairCom RTG utilities list xddgen).
- Ensure you are using the XDD that belongs to the specific data file/version you are inspecting.
Windows shows 'Choose an app to open this file'
.xdd is not a widely registered consumer format and may not have a default association. Also, multiple unrelated programs can use the same extension.
- Open it with a text/XML editor first to determine whether it is an RTG XDD XML schema.
- If it is RTG/COBOL-related, install/use the FairCom RTG utilities or the COBOL-IT tool that expects an XDD file (e.g., Data Displayer workflow referenced in COBOL-IT docs).
Security note
FairCom RTG XDD files are XML; treat .xdd from untrusted sources as untrusted input for XML parsers and for any tooling that will use it to interpret/drive access to data files (a maliciously crafted schema could trigger edge cases in parsers).