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Choosing a 32-bit or 64-bit ClearCase offering for Linux x86_64 hosts

Question & Answer


What should I consider when choosing between a 32-bit or 64-bit IBM Rational ClearCase offering to install on Linux x86_64 hosts?


In releases before version 9.0.1, ClearCase provides only a 32-bit Linux x86 offering that is compatible with both 32-bit and 64-bit x86 operating systems. That offering uses either a 32-bit or 64-bit MVFS kernel module (selected automatically to match the operating system's kernel mode). All other code uses 32-bit mode: ratlperl, Java runtime, GUIs, command line tools, utilities, and so forth.

As of release 9.0.1, ClearCase provides two installation offerings that can run on Linux x86_64 hosts:

  • The original Linux x86 offering is available with the same 32-bit code for ClearCase (selecting the proper MVFS) when run on a 64-bit host.
  • The new Linux x86_64 offering in release 9.0.1 supports only 64-bit (x86_64) operating systems. All code runs in 64-bit mode, except for programs that dump old format view databases.

When to choose the x86 offering

  • Required if you are using a 32-bit kernel.
  • Optional if you are using a 64-bit kernel.
  • If you are upgrading from earlier ClearCase releases and do not have a specific need for 64-bit mode.
  • If you are upgrading within Installation Manager and do not want to uninstall and then reinstall ClearCase.
  • If you are using binary integrations with your own 32-bit applications (for example, the ClearCase Perl extension CtCmd perl package built for your own perl).
  • If you are using ratlperl to load your own extensions with native code built as 32-bit shared libraries.

When to choose the x86_64 offering

  • Prerequisite: Using a 64-bit kernel on an x86_64 machine.
  • If you want to reduce the number of 32-bit compatibility system libraries required for ClearCase.
  • If you want to use a 64-bit ratlperl (or your own perl) with a compatible CtCmd module.

Notes (updated for fix pack and later)


  • If your system currently has a 32-bit offering of a ClearCase release installed, and you want to install the 64-bit offering, you must uninstall the prior release, then install the 64-bit offering of the new release.
  • You can only install one ClearCase offering at a time.
  • The view database format is compatible between the two offerings. You do not need to reformat view databases stored on your hosts if you switch between x86 and x86_64 offerings.
  • Release 9.0.1 and fix packs and have VOB database formats that are incompatible between 32-bit and 64-bit offerings. 64-bit platforms in fix packs and have a different VOB database format than 9.0.1. For complete details on how to handle the VOB databases in these fix packs, see technote 2004783.
  • Fix pack and later have a VOB database format that is compatible between the 32-bit and 64-bit offerings. You do not need to reformat VOB databases when switching between the offerings at this fix pack level.
  • Installation Manager can be 32-bit or 64-bit. Either version can install whichever ClearCase offering you want on x86_64 hosts.
  • To review the required system packages when installing the 64-bit offering, see technote 2003747.


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Document Information

Modified date:
09 August 2018