The choice of the wrapper depends on the integration method used for each of the tools. These methods are three: encapsulation, instrumentation, interception. The following table summarizes the ways to invoke the wrappers:

Technique Wrapper Description
Interception vrt Use this to also activate interception of the operating system calls. The wrapper also honors encapsulation and instrumentation. The interception is available only on Linux.
Instrumentation vov Use this wrapper for tools that have been instrumented. The wrapper also honors encapsulation, if available.
Encapsulation vw Use this wrapper for tools that have been encapsulated. If no capsule is available, then the only input is the "executable" and the only output is the stdout and stderr, or any redirection thereof. This wrapper is also used in Accelerator for batch jobs.

The binaries vovbuild, clevercopy, and cleverrename don't need to be run with a wrapper usually as they are fully instrumented. In the rare case of slow NFS servers, a vov wrapper may be needed.

Note: There is only one actual binary which all wrappers invoke to activate runtime tracing, and it is called vw2. Through symbolic links (on UNIX) or copies, the binary can be called with several different names. The behavior of the wrapper is controlled either by the name used to invoke the binary or by the command line options -C, -V, -R and -T.