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| Chapter 6 PLV: Top-Level Constants and Functions |

## 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.

6.5 The Predefined Datatypes |  | 7. p: A Powerful Substitute for DBMS_OUTPUT

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