Identifying VOBs and subfolders for migration

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You must plan what Rational® ClearCase® files and folders to migrate. With the ClearCase Version Importer, you can specify either a VOB root or a folder from which to export the data.

About this task

Importing a large volume of data can take a significant amount of time and might affect the Jazz® Team Server performance after the import. A good practice is to identify what you need to import, rather than attempting to import everything in Rational ClearCase.
When you evaluate the volume of data, the number of versions in the VOB is an important factor that impacts the duration of the import. You can run the following Rational ClearCase command to get the number of versions:
cleartool lshistory -recurse <root path to import>
Use the Linux word count (wc) command or a text editor to count the number of output lines that are generated.
A good practice is to ensure that the total number of files and folders per component of IBM® Engineering Workflow Management (EWM) source control does not exceed 100,000. For more information, see Collaborative Lifecycle Management 2012 Sizing Report (Standard Topology E1). When you plan to migrate a Rational ClearCase VOB that has more than 100,000 files and folders, you can split it into multiple EWM components. Even if it does not exceed 100,000 files and folders, a good practice is to identify the subfolders in a VOB, which distinguishes it as a component, and then import the subfolders to separate EWM components. As a result, you can do the following actions:
  • Migrate the data in separate components, in parallel, to accelerate the migration.
  • Maintain the code easily after the migration by creating an individual baseline, or adding and removing individual components in the stream.
  • Configure different hardware and software environments from the topology in the sizing report (100,000 files per component might exceed your project needs).
To assess the number of files and folders in a VOB, run the following Rational ClearCase command:
cleartool ls -recurse <root path to import>
Use the Linux word count (wc) command or a text editor to count the number of output lines that are generated.
Note: As an alternative, you can use the Rational ClearCase database utility, countdb, to assess how many elements or versions are in the Rational ClearCase VOB. The count might not reflect the number of elements or versions to be migrated for the following reasons:
  • The ClearCase Version Importer does not import directory versions.
  • The element count that is determined with the countdb utility is the total number of file elements, directory elements, and symbolic link elements.
  • The element count is the total number of elements for the VOB. When you migrate a subfolder, the number might be smaller.
  • Both the version count and the element count that is determined with the countdb utility is the total number of versions and elements for the VOB respectively. When you migrate a subfolder, you select a subset to export and import, so the numbers might be smaller.
You can also migrate the Rational ClearCase versions selectively by specifying one of filtering options. For more information, see Selecting versions to export by filtering.
When you import multiple VOBs, use the following guidelines:
  • You must run the export and the import command for each VOB. You can run the export commands at the same time, but you must specify different data output folders each time you run the command. You can expedite the export step by running commands at the same time for multiple VOBs.
  • When you create multiple components from one Rational ClearCase VOB, you must create separate intermediate data for each EWM component. You can specify a subfolder as a root to extract data from (rather than a VOB root) when you run the export command.

What to do next

After subfolders are exported, the root can be exported as a way to migrate large numbers of files in smaller increments. For more information, see Migrating data in increments.