Necessary Supplied Packages
In this section of the book, we will cover the supplied database packages that, in my opinion, everyone
needs to be aware of. Each of these packages is documented in the Oracle document entitled Oracle8i
Supplied PL/SQL Packages Reference. The supplied documentation typically shows the entry points
(externalized procedures and functions) of the supplied package, and gives you an overview of each
function/procedure's usage. In this section we will describe in more detail when you might (or might
not) choose to use such a package. We will not go into depth on each and every procedure in every
package. Rather, we will discuss the most commonly used package entry points, and show how they are
used. For a comprehensive list of all procedures available in a given package, along with all possible
parameters, I will refer you to the aforementioned document.
This appendix will serve as a 'jumping off' point for using these supplied packages. After you are done
with it, you will have a good feel for the intended use of many of them. We do not cover every supplied
package in this section. This does not imply that they are not useful, just that their use falls outside the
scope of typical development. We will explore the packages that applications will employ in most cases.
The packages we will cover are:
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❑
DBMS_ALERT and DBMS_PIPE – Inter-process communication facilities in the database.
DBMS_ALERT can be used to signal all interested sessions that some event has taken place.
DBMS_PIPE allows two sessions to 'talk' to each other, much like a TCP/IP socket.
❑
DBMS_APPLICATION_INFO – Allows an application to register useful information in the V$
tables. Extremely useful to monitor what your stored procedure is doing, and register other
information.
❑
DBMS_JAVA – A PL/SQL package useful for working with Java stored procedures.
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Appendix A
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DBMS_JOB – A database job scheduler. Used when you have that stored procedure you want
to execute every night at 2am, or when you just want to run something in the background.
❑
DBMS_LOB – For working with Large OBjects (LOBs) in the database.
❑
DBMS_LOCK – To create your own user-defined locks, separate and distinct from Oracle's row
row or table level locks.
❑
DBMS_LOGMNR – To review and analyze the contents of your online redo log files
❑
DBMS_OBFUSCATION_TOOLKIT – Provides data encryption in the database.
❑
DBMS_OUTPUT – Provides simple screen I/O capabilities for PL/SQL in SQL*PLUS and
SVRMGRL.
❑
DBMS_PROFILER – A PL/SQL source code profiler built into the database.
❑
DBMS_UTILITY – A 'hodge-podge' collection of useful procedures.
❑
UTL_FILE – Provides text file I/O for PL/SQL. Allows PL/SQL to read and write text files on
the server.
❑
UTL_HTTP – Provides access to the HTTP (Hyper Text Transfer Protocol) protocol from
within PL/SQL. Allows PL/SQL to 'grab' web pages.
❑
UTL_RAW – Provides conversion between the RAW and VARCHAR2 types. Extremely useful
when working with TCP/IP, BLOBs and BFILEs, and encryption.
❑
UTL_SMTP – Provides access to the SMTP (Simple Mail Transfer Protocol) from within
PL/SQL. Specifically, it allows you to send an e-mail from PL/SQL.
❑
UTL_TCP –Provide TCP/IP socket abilities for PL/SQL. Allows PL/SQL to open a connection
to any TCP/IP service.
Why Use the Supplied Packages?
The reasoning behind using the supplied packages is simple, it is much easier and more maintainable to
develop using supplied functionality then it is to build your own. If Oracle supplies a package for doing
something (for example, data encryption) it would not be productive to write your own. Often, I find
people implementing functionality that they did not know already existed in the database, purely out of
ignorance. Knowing what tools you have available to you will make your life much easier.
About The Supplied Packages
The supplied packages from Oracle all begin with either DBMS_ or UTL_. Historically, packages that
were created by Server Technologies (the guys who write the database) begin with DBMS_. The UTL_
packages were derived from other sources. The UTL_HTTP package, for performing HTTP calls from
PL/SQL (to retrieve web pages and such), is an example of such an external package. The Application
Server Division at Oracle developed this package in order to support the concept of ICX (InterCartridge eXchange) with OAS (the Oracle Application Server), which has now been replaced with iAS,
(the internet Application Server). This naming difference does not mean anything to us, the developers,
really – it is just interesting to note.
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Necessary Supplied Packages
Most of these packages are stored in a compiled, wrapped format in the database. This wrapped format
protects the code from snooping eyes. We can see the specification of the code but we cannot see the
code itself. If you were to select the code of DBMS_OUTPUT PACKAGE BODY from the database itself, it
might look like something like this:
tkyte@TKYTE816> select text
2 from all_source
3 where name = 'DBMS_OUTPUT'
4 and type = 'PACKAGE BODY'
5 and line < 10
6 order by line
7 /
TEXT
-----------------------------------------package body dbms_output wrapped
0
abcd
abcd
abcd
abcd
abcd
abcd
abcd
9 rows selected.
Not very useful. What is very useful however, is if we select out the specification of the PACKAGE:
tkyte@TKYTE816> select text
2
from all_source
3
where name = 'DBMS_OUTPUT'
4
and type = 'PACKAGE'
5
and line < 26
6
order by line
7 /
TEXT
-------------------------------------------------------------------------package dbms_output as
------------- OVERVIEW
--- These procedures accumulate information in a buffer (via "put" and
-- "put_line") so that it can be retrieved out later (via "get_line" or
-- "get_lines"). If this package is disabled then all
-- calls to this package are simply ignored. This way, these routines
-- are only active when the client is one that is able to deal with the
-- information. This is good for debugging, or SP's that want to want
-- to display messages or reports to sql*dba or plus (like 'describing
-- procedures', etc.). The default buffer size is 20000 bytes. The
-- minimum is 2000 and the maximum is 1,000,000.
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Appendix A
------------ EXAMPLE
--- A trigger might want to print out some debugging information. To do
-- do this the trigger would do
-dbms_output.put_line('I got here:'||:new.col||' is the new value');
-- If the client had enabled the dbms_output package then this put_line
-- would be buffered and the client could, after executing the statement
-- (presumably some insert, delete or update that caused the trigger to
-- fire) execute
25 rows selected.
Hidden in the database is an online source of documentation. Each of these packages has a specification
that has a nice overview of what the package is, what each function or procedure does, and how to use
it. This is obviously very handy when you don't have the documentation, but is also useful even when
you do, since the specification sometimes contains data that the documentation doesn't mention, or has
further examples that are useful.
We will now look at the various packages I find useful in day-to-day work with Oracle. These are the
packages, which not only I use frequently, but find others using as well. Additionally, we'll introduce
some new packages, or ways to do things to work around some of the limitations of these built-in
packages – limits people frequently hit, in my experience.
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