[Chapter 6] 6.6 The Predefined Constants

6.6 The Predefined Constants

In addition to the predefined datatypes, the PLV package offers a set of constants that are used throughout PL/Vision. These constants define the type of input or output repository you want to use in a given situation. These constants are used in PLVio, PLVlog, and PLVexc. The input/output options in PL/Vision are shown in the following table.

Description	Constant
Database table	`dbtab`
PL/SQL table	`pstab`
Operating system file	`file`
VARCHAR2 string	`string`
Standard output	`stdout`

For example, if you want to define the target repository of the PLVio package to be a PL/SQL table, you will issue this command:

SQL> exec PLVio.settrg (PLV.pstab);

If you want PLVlog to write its information to an operating system file, you will execute this command:

SQL> exec PLVlog.tofile;

which in turn sets the v_log_type variable to the PLV.file constant.

Once you build a package like this, you will find yourself constantly adding to it. Be careful not to throw in constants and programs that really do have a place in another, less generic package.

The boolstg , errm , and now functions of PLV can all be used from within SQL statements, since the package specification for PLV includes calls to the RESTRICT_REFERENCES pragma.

The errm function is a good example of how you can use a layer of your own PL/SQL code around native PL/SQL builtins (SQLERRM) to make the information more widely accessible (i.e., callable from within SQL statements) .

6.6 The Predefined Constants

Special Notes on PLV