Advanced Oracle PL/SQL Programming with Packages

9.1. PLVmsg Data Structures

The PL/SQL table used by PLVmsg to store message text is defined in the package body as follows:

msgtxt_table PLVtab.vc2000_table;

A PLVmsg message can therefore have a maximum of 2,000 bytes in the text.

The rows in this PL/SQL table are not filled sequentially. The rows are the message numbers and might represent Oracle error numbers, an entity's primary key values, or anything else the user passes as the message number. As a result (for PL/SQL Releases 2.2 and earlier), the PLVmsg package must keep track of the lowest and highest number rows. These values are stored in the following private variables:

v_min_row BINARY_INTEGER;
v_max_row BINARY_INTEGER;

Note that a user of PLVmsg cannot make a direct reference to the msgtxt_table or the low and high row values; these data structures are hidden in the package body. I am, in this way, able to guarantee the integrity of the message text.