Advanced Oracle PL/SQL Programming with Packages

21.2. PLVtrc: Tracing Execution of PL/SQL Programs

The PLVtrc (PL/Vision TRaCe) package offers a generic trace facility for PL/SQL applications. It is especially useful if you do not have access to a source debugger for PL/SQL. It is also used by PLVexc to record the currently executing PL/SQL program unit when an exception occurs.

The PLVtrc package offers several capabilities:

• Provides a flexible execution trace facility. It inserts trace points anywhere in your code; these fire and display (or write to a log) only if you explicitly turn on the trace. Thus, your trace can remain in place even in production code.

• Parses the string returned by a call to the DBMS_UTILITY.FORMAT_CALL_STACK function. You can specify retrieval of the nth module in the stack and use this information in your own auditing and trace activities.

• Is similar to the p package. PLVtrc offers a heavily overloaded interface to the PUT_LINE procedure of DBMS_OUTPUT. (In fact, PLVtrc calls the p.l procedure to generate its output.)

The elements provided by PLVtrc can be broken down into three areas: output control, module tracking, and activity trace. They are explored in the following sections.

21.2.1. Directing Output from PLVtrc

As with many other PL/Vision packages, PLVtrc allows you to programmatically control its behavior, in this case its output. PLVtrc offers three different types of output:

• Display the trace message to the screen. If not turned on, all calls to PLVtrc programs are ignored.

• Log the trace ...