Editing DTrace (section)

== Description ==
Sun Microsystems designed DTrace to give operational insights that allow users to tune and troubleshoot applications and the OS itself.

Testers write tracing programs (also referred to as scripts) using the D programming language (not to be confused with other [[D programming language (disambiguation)|programming languages named "D"]]).  The language, inspired by [[C (programming language)|C]], includes added functions and variables specific to tracing. D programs resemble [[AWK]] programs in structure; they consist of a list of one or more ''probes'' (instrumentation points), and each probe is associated with an action. These probes are comparable to a [[pointcut]] in [[aspect-oriented programming]]. Whenever the condition for the probe is met, the associated action is executed (the probe "fires"). A typical probe might fire when a certain file is opened, or a process is started, or a certain line of code is executed. A probe that fires may analyze the run-time situation by accessing the [[call stack]] and context variables and evaluating expressions; it can then print out or log some information, record it in a database, or modify context variables. The reading and writing of context variables allows probes to pass information to each other, allowing them to cooperatively analyze the correlation of different events.

Special consideration has been taken to make DTrace safe to use in a production environment. For example, there is minimal [[probe effect]] when tracing is underway, and no performance impact associated with any disabled probe; this is important since there are tens of thousands of DTrace probes that can be enabled. New probes can also be created dynamically.