12.2 Restrictions on Multiple Replicas in a LAN

You must observe these restrictions when using multiple replicas in a local area network:

• Do not register multiple replicas of a VOB family in a single region.

This restriction prevents multiple replicas from being mounted on a host and prevents developers from accessing multiple replicas of a VOB family with a single view.

• Locate cross-VOB symbolic links in branched directories.

NOTE: If the leaf name of the UNIX VOB-tag is the same as the Windows VOB-tag (for example, /vobs/dev and \dev), this restriction does not apply.

Cross-VOB symbolic links point to particular replicas. To make it possible for clients to use a different replica, you can branch the directory that contains the symbolic link. Branching the directory may lead to partitioning replica use based on projects.

For example, assume a project uses the branch v2.0_integration as the integration branch and the directory vob_links contains all the symbolic links that cross VOBs. The project manager creates a v2.0_integration branch of the directory vob_links, and then adjusts any symbolic links to point to the VOB-tag of the replica in use for that project. For example, on UNIX:

ls -l
tests -> ../../tests
gui_src -> ../../gui_src
design -> ../../design

On Windows:

cleartool ls
tests -> ../../tests
gui_src -> ../../gui_src
design -> ../../design

The leaf name of the VOB-tag of the local replica is gui_src_replica2, so the project manager adjusts the symbolic links as follows:

cleartool checkout -nc .
cleartool rmname gui_src
cleartool ln -s ../../gui_src_replica2 gui_src
cleartool checkin .

This ensures that the correct replica is referenced during a build of this project.

You can also use one symbolic link that refers to another VOB and have other symbolic links refer to it. For example:

rational_install -> ../../vobs/rational/install
release_list -> rational_install/release_list

This limits the number of duplicate links that must be maintained. We also recommend that you avoid cross-VOB symbolic links as much as possible.

• Make sure case-sensitivity and text mode settings are correct.

You must make sure that case-sensitivity and the text mode are handled properly. If there are case conflicts among files at different replicas, errors occur during synchronization. The text mode controls the use of line terminators in files; differences in use of line terminators between UNIX and Windows editors cause unexpected behavior during file comparisons and merges.

The Administrator's Guide for Rational ClearCase describes how to handle case-sensitivity and text mode setup. Be sure to read it carefully before creating UNIX and Windows replicas.

CAUTION: Do not use MultiSite to create multiple copies of a VOB in a single ClearCase region. Because the VOB UUID is identical for all replicas in a VOB family and is stored in many structures within a VOB, there is no way to make the copy of the VOB unique. Creating and using multiple copies of a VOB in a single region causes clearmake and views to exhibit unpredictable behavior, may cause data loss, and is not supported by Rational Software.