Can you let me know your Oracle Server version, and the type of variable you are trying to view (global/local, private/public, scalar/compound)?
Note that the debugger can only display scalar datatypes (varchar2, number, date, ...) or collections of a scalar data type. It cannot display compound datatypes like records or object types.
Also note that Oracle Server 8.0.4 and earlier does not support global package variables (private or public).
Furthermore, if only the specification or body of a package is compiled "with debug information" then this error message can also occur. In that case you can explicitly add debug information by right-clicking on the package in the Object Browser or in a source file, and selecting "Add debug information" from the popup menu.
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Marco Kalter
Allround Automations