[Appendix C] Built-In PackagesAppendix C C. Built-In PackagesContents:Using the Built-in PackagesDBMS_ALERTOracle AQ, the Advanced Queueing FacilityDBMS_DDLDBMS_ JOBDBMS_LOB (PL/SQL8 Only)DBMS_LOCKDBMS_MAILDBMS_OUTPUTDBMS_PIPEDBMS_ROWID (PL/SQL8 Only)DBMS_SESSIONDBMS_SNAPSHOTDBMS_SQLDBMS_TRANSACTIONDBMS_UTILITYUTL_FILEThis appendix provides a quicksummary of the most commonly used RDBMS-based packages built by Oracle Corporation and made available to all developers. Table C.1 shows the list of packages covered here. Unless otherwise noted, the packages are available in PL/SQL Release 2.1 and above. Table C.1: Built-In Packages Stored in the Oracle Database Package Name Description DBMS_ALERT Provides support for notification of database events on an asynchronous basis. Registers a process with an alert and then waits for a signal from that alert. DBMS_AQ Offers an interface to Oracle/AQ, the Advanced Queueing Facility of Oracle8 (PL/SQL8 only). DBMS_AQADM Used to perform administrative tasks for Oracle/AQ (PL/SQL8 only). DBMS_DDL Provides programmatic access to some of the SQL DDL statements. DBMS_JOB Submits and manages regularly scheduled jobs for execution inside the database (PL/SQL Release 2.1) DBMS_LOB Provides a set of programs to manipulate LOBs (large objects) (PL/SQL8 only). DBMS_LOCK Lets you create your own user locks in the database. DBMS_MAIL Interfaces to Oracle Office (formerly known as Oracle*Mail). DBMS_OUTPUT Displays output from PL/SQL programs to the terminal. DBMS_PIPE Communicates between different Oracle sessions through a pipe in the RDBMS shared memory. DBMS_ROWID Encapsulates information about the structure of the ROWID datatype and allows for conversion between restricted and extended ROWIDs (PL/SQL8 only). DBMS_SESSION Provides a programmatic interface to several SQL ALTER SESSION commands and other session-level commands. DBMS_SNAPSHOT Provides a programmatic interface through which you can manage snapshots and purge snapshot logs. You might use modules in this package to build scripts to automate maintenance of snapshots. DBMS_SQL Provides full support for dynamic SQL within PL/SQL. Dynamic SQL refers to statements that are not prewritten into your programs. They are, instead, constructed at run time as character strings and then passed to the SQL engine for execution. (PL/SQL Release 2.1) DBMS_ TRANSACTION Provides a programmatic interface to a number of the SQL transaction statements, such as SET TRANSACTION. DBMS_UTILITY The miscellaneous package. Contains various useful utilities, such as FORMAT_CALL_STACK, which returns the current stack of called modules. UTL_FILE Allows PL/SQL programs to read from and write to operating system files. (PL/SQL Release 2.3) All of the packages in Table C.1 are stored in the database and can be executed both by client- and server-based PL/SQL programs. In addition to these packages, many of the development tools, like Oracle Forms, offer their own specific package extensions, such as packages to manage OLE2 objects and DDE communication.[1] [1] For more detailed information about these built-in packages, see my book, Oracle Built-in Packages. C.1 Using the Built-in PackagesIn this appendix, I've provided a brief overview of each package, followed by a description and header for each program in the package. These headers are structured as follows: PROCEDURE pkg.procname (<parameter list>); FUNCTION pkg.funcname (<parameter list>) RETURN <return datatype>;where pkg is the name of the package, procname and funcname are the names of the programs, <parameter list> is the list of parameters (if there are no parameters, then you do not provide parentheses either) and <return datatype> is the datatype of the value returned by the function. Let's look at an example. Suppose that you want to receive a message from a pipe. The header for the built-in function which does this is: FUNCTION DBMS_PIPE.RECEIVE_MESSAGE=20 (pipename IN VARCHAR2, timeout INTEGER DEFAULT DBMS_PIPE.MAXWAIT) RETURN INTEGER;Note that all identifiers are in uppercase except for parameter names. This is consistent with my conventions: all keywords and other identifiers built by Oracle are in uppercase. The parameter names are lowercase because in many program headers, I have provided my own parameter names to make the headers more readable. When I want to call a packaged program, I must use dot notation. For example to make use of the RECEIVE_MESSAGE built-in, I would write code like this: DECLARE pipe_status INTEGER; BEGIN pipe_status DBMS_PIPE.RECEIVE_MESSAGE (mypipe, 10); END;B.2 Restrictions on Calling Stored ProceduresC.2 DBMS_ALERT Copyright (c) 2000 O'Reilly & Associates. All rights reserved.