Oracle Packages

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About the DBMS_PIPE Package

Package DBMS_PIPE allows different sessions to communicate over named pipes. (A pipe is an area of memory used by one process to pass information to another.) You can use the procedures PACK_MESSAGE and SEND_MESSAGE to pack a message into a pipe, then send it to another session in the same instance or to a waiting application such as a UNIX program.

At the other end of the pipe, you can use the procedures RECEIVE_MESSAGE and UNPACK_MESSAGE to receive and unpack (read) the message. Named pipes are useful in many ways. For example, you can write a C program to collect data, then send it through pipes to stored procedures in an Oracle database.

About the HTF and HTP Packages

Packages HTF and HTP allow your PL/SQL programs to generate HTML tags.

About the UTL_FILE Package

Package UTL_FILE lets PL/SQL programs read and write operating system (OS) text files. It provides a restricted version of standard OS stream file I/O, including open, put, get, and close operations.

When you want to read or write a text file, you call the function FOPEN, which returns a file handle for use in subsequent procedure calls. For example, the procedure PUT_LINE writes a text string and line terminator to an open file, and the procedure GET_LINE reads a line of text from an open file into an output buffer.

About the UTL_HTTP Package

Package UTL_HTTP allows your PL/SQL programs to make hypertext transfer protocol (HTTP) callouts. It can retrieve data from the Internet or call Oracle Web Server cartridges. The package has two entry points, each of which accepts a URL (uniform resource locator) string, contacts the specified site, and returns the requested data, which is usually in hypertext markup language (HTML) format.

About the UTL_SMTP Package

Package UTL_SMTP allows your PL/SQL programs to send electronic mails (emails) over Simple Mail Transfer Protocol (SMTP). The package provides interfaces to the SMTP commands for an email client to dispatch emails to a SMTP server.

Guidelines for Writing Packages

When writing packages, keep them general so they can be reused in future applications. Become familiar with the Oracle-supplied packages, and avoid writing packages that duplicate features already provided by Oracle.

Design and define package specs before the package bodies. Place in a spec only those things that must be visible to calling programs. That way, other developers cannot build unsafe dependencies on your implementation details.

To reduce the need for recompiling when code is changed, place as few items as possible in a package spec. Changes to a package body do not require recompiling calling procedures. Changes to a package spec require Oracle to recompile every stored subprogram that references the package.

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