7.1 ClearCase LT Server Configuration Guidelines

The ClearCase LT server must be appropriately configured for the number and size of VOBs it supports. Server configuration is critical to obtaining satisfactory performance.

NOTE: ClearCase has special requirements for the Windows domain membership of the ClearCase LT server and ClearCase LT users. See Chapter 4, ClearCase and Windows Domains.

The computer chosen as the ClearCase LT server must satisfy these requirements:

• Main memory (RAM). The minimum recommended main memory size is 128 MB or half the size of all the VOB databases the server will host, whichever is greater. To this amount, add 7 MB of memory per VOB, regardless of VOB database size, as well as 750 KB of memory for each view that the ClearCase LT server will support. Adequate physical memory is the most important factor in VOB performance; increasing the size of a VOB host's main memory is the easiest (and most cost-efficient) way to make VOB access faster and to increase the number of concurrent users without degrading performance. For the best performance, configure the ClearCase LT server with enough main memory to hold the entire VOB database of all the VOBs you plan to create.

• Disk capacity. A VOB database must fit in a single disk partition, and VOB databases tend to grow significantly as development proceeds and projects mature. We recommend a high- performance disk subsystem, one with high rotational speed, low seek times, and a capacity of at least 10 GB.

If possible, use a RAID or similar disk subsystem that takes advantage of disk striping and mirroring. Mirrors are useful for backups, although there is a slight performance degradation associated with their use. However, striping helps overall performance and more than makes up for any degradation caused by mirroring. For more information, see Maximize Disk Performance.

• Processing power. A ClearCase LT server must have adequate CPU capacity. The definition of adequate in this context varies from one hardware architecture to another. With ClearCase and similar enterprise applications, server CPU capacity is a critical factor governing performance of client operations. Make the most of the available server CPU cycles by keeping nonessential processes-including ClearCase client tools and views-off the ClearCase LT server.

See also Chapter 19, Improving VOB Host Performance.

VOB Feature Levels

A feature level is an integer that defines the set of features that a VOB supports. Whenever a ClearCase LT release introduces features that require support in the VOB database, you must raise the feature level of a VOB before clients can take advantage of the new features when accessing data in that VOB.Every ClearCase release is associated with a feature level. See the Release Notes for ClearCase LT for information on which feature levels a release supports.

Displaying the Feature Level

To display the feature level of a VOB, use the Windows explorer or ClearCase Administration Console to display the properties of the VOB. The feature level is listed on the Custom tab. You can also use the cleartool command line.

cleartool describe vob:\dev
versioned object base "\dev"
created 15-Aug-00.14:19:03 by Susan Goechs (susan.user@minuteman)
VOB family feature level: 2
...

Changing the Feature Level

The chflevel command changes the feature level of a VOB. To raise the feature level of a VOB:

1. Log on to the ClearCase LT server.

2. Issue the chflevel command with the -auto option. The command lists each VOB served by the host. It then offers to raise the feature level of each VOB that is not already at the feature level corresponding to the release of ClearCase LT that is installed on the server.

VOB Schema Versions

Every VOB has a database schema version that denotes the format of the VOB database, and determines the types of data the VOB can accommodate. There are two schema versions:

• Schema version 53, which has been supported by every ClearCase release since 3.0, but is not supported by ClearCase LT

• Schema version 54, which provides better support for Windows security identifiers and is required when using ClearCase in an Active Directory environment. Schema version 54 also provides support for larger VOB database files (greater than 2 GB) on certain platforms.

All VOBs on a VOB server host must be formatted with the same schema version. When you install ClearCase server software on a host, you are prompted to select a schema version to be used by VOBs created on that host.

To change the schema version of an existing VOB to a higher-numbered schema version, use the reformatvob command. You cannot reformat a VOB to a lower-numbered schema version.