About Exporting the Delta Data

The export import feature lets you create a delta set of objects that have changed between one export and another. This enables an incremental export import which can save time and disk space.

The Delta Workflow

A delta contains either job information or calendar information. The delta function should normally be used when comparing two versions of exported data stored in a configuration management system.

The delta process does not produce a friendly diff if it is used to compare exports from a source and a destination system because of the mapping differences. Instead, use the -CO import option to compare the source and destination during import.

When the command for creating and exporting a delta is invoked, this happens:

  1. Two versions of export directories are checked to ensure that they only have files that can be identified by the utility. If there are files in either version that the utility cannot identify, processing stops after logging an error.

  2. The directory specified to output the delta to should either be empty or not exist, or else the utility stops processing after logging an error. If the output directory does not exist the utility creates it. Therefore, the Export Import utility requires file system permissions to be able to create a directory.

  3. The delta process compares each artifact in two versions of the data and outputs the delta information:

    • Matching data – If an artifact in the two versions match, this artifact is not included in the delta.

    • Updated data – If the artifacts in the <export-directory-V1> and the <export-directory-V1> do not match, the artifact from the <export-directory-V2> is included in the delta.

    • New data – If an artifact is in the <export-directory-V2>, but is not in the <export-directory-V1>, it is included in the delta.

    • Deleted data – If an artifact is in the <export-directory-V1> but is not in the <export-directory-V2>, it is marked for deletion in the delta.

  1. The delta is output as XML. The delta output retains the XML structure of the source or destination artifacts while marking them with modifiers indicating whether the artifacts should be created, updated, or deleted.

    The structure of the delta XML output:

  1. If an error is encountered during the delta process, the utility quits processing. The utility does not clean or remove data that was already output up to the point of error so that analysis of the error that can occur.

  2. Once the delta is successfully done and written to the file system as XML files, the utility writes a file named export.log to the output directory to record summary information about the delta.

    The summary information in the delta export.log includes:

    • Type of delta (job or calendar)

    • The version of the TA Master

    • The time taken for export

The “delta” folder contains the delta information between source and destination repositories (or between repository version-2 and repository version-1). The source folder contains the entire content of the source repository so that the context for the delta information can be maintained.

Note: Some static data is exported for the purpose of providing the context for the exported data. Delta of static data is not done.