The Statically Defined Tracing (SDT) provider creates probes at sites that a software programmer has formally designated. The SDT mechanism allows programmers to consciously choose locations of interest to users of DTrace and to convey some semantic knowledge about each location through the probe name. The Oracle Solaris kernel has defined a handful of SDT probes, and will likely add more over time. DTrace also provides a mechanism for user application developers to define static probes, described in Chapter 13, Statically Defined Tracing for User Applications.