SIZE(K) KEPT NAME −−−−−− −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− −−−−−−−−−−−−−− 180 SYS.STANDARD (PACKAGE) 78 YES QDBA.Q$CVAR (PACKAGE) 74 SELECT JOB FROM SYS.DBA_JOBS_RUNNING WHERE JOB = :b1 (0F884588,518752523) (CURSOR) 71 YES QDBA.Q$INSTAT (PACKAGE BODY) 62 YES QDBA.Q$BGPROC (PACKAGE BODY) PL/SQL procedure successfully completed. SQL> execute dbms_shared_pool.keep('0F884588,518752523','C'); PL/SQL procedure successfully completed. SQL> execute dbms_shared_pool.sizes(50); SIZE(K) KEPT NAME SIZE(K) KEPT NAME −−−−−− −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− −−−−−−−−−−−−−− 180 SYS.STANDARD (PACKAGE) 78 YES QDBA.Q$CVAR (PACKAGE) 74 YES(1) SELECT JOB FROM SYS.DBA_JOBS_RUNNING WHERE JOB = :b1 (0F884588,518752523) (CURSOR) 71 YES QDBA.Q$INSTAT (PACKAGE BODY) 62 YES QDBA.Q$BGPROC (PACKAGE BODY) PL/SQL procedure successfully completed. After the cursor is pinned, the second call to the SIZES procedure indicates this by showing "YES" in the KEPT output column. It is interesting (and somewhat confusing) that such a simple SELECT statement results in a cursor that uses 74K of shared pool memory. 12.2.4.3 The DBA_KEEPSIZES view DBA_KEEPSIZES is a view that makes available the size PL/SQL objects will occupy in the shared pool when kept using the DBMS_SHARED_POOL.KEEP procedure. This view can be used by the DBA to plan for shared pool memory requirements of large PL/SQL objects. The actual view definition, contained in the dbmspool.plb file, follows: CREATE OR REPLACE VIEW DBA_KEEPSIZES (totsize, owner, name) AS SELECT TRUNC((SUM(parsed_size)+SUM(code_size))/1000) ,owner ,name FROM dba_object_size WHERE TYPE IN ('PACKAGE','PROCEDURE','FUNCTION','PACKAGE BODY','TRIGGER') GROUP BY owner, name; The columns for DBA_KEEPSIZES are defined in the following table. Column Datatype Description TOTSIZE NUMBER Size in shared pool if object kept (via KEEP) OWNER VARCHAR2(30) Schema of the stored PL/SQL object NAME VARCHAR2(30) Name of the stored PL/SQL object You can query DBA_KEEPSIZES to get an idea of which packages, procedures, and functions are relatively [Appendix A] What's on the Companion Disk? 12.2.4 DBMS_SHARED_POOL Examples 571 large, and thus may be good candidates for pinning into the shared pool. 12.1 DBMS_SPACE: Obtaining Space Information 13. Job Scheduling in the Database Copyright (c) 2000 O'Reilly & Associates. All rights reserved. [Appendix A] What's on the Companion Disk? 12.2.4 DBMS_SHARED_POOL Examples 572 Chapter 13 573 13. Job Scheduling in the Database Contents: Getting Started with DBMS_ JOB Job Queue Architecture Tips on Using DBMS_JOB DBMS_JOB Examples The DBMS_JOB package is actually an API into an Oracle subsystem known as the job queue. The Oracle job queue allows for the scheduling and execution of PL/SQL routines (jobs) at predefined times and/or repeated job execution at regular intervals. The DBMS_JOB package provides programs for submitting and executing jobs, changing job execution parameters, and removing or temporarily suspending job execution. This package is the only interface with the Oracle job queue. DBMS_JOB is used to schedule many different types of tasks that can be performed in PL/SQL and that require regular execution. The job queue is used extensively by Oracle replication facilities, and was originally developed for the purpose of refreshing Oracle snapshots. DBMS_JOB is often used by DBAs to schedule regular maintenance activities on databases, typically during periods of low usage by end users. It can similarly be used by applications to schedule large batch operations during off hours. The job queue can also be used to start up service programs that listen on database pipes and respond to service requests by user sessions. 13.1 Getting Started with DBMS_ JOB The DBMS_JOB package is created when the Oracle database is installed. The dbmsjob.sql script (found in the built−in packages source code directory, as described in Chapter 1, Introduction) contains the source code for this package's specification. This script is called by catproc.sql, which is normally run immediately after database creation. The script creates the public synonym DBMS_JOB for the package and grants EXECUTE privilege on the package to public. All Oracle users can reference and make use of this package. There are several data dictionary views that display information about the Oracle job queue. These are called DBA_JOBS, USER_JOBS, and DBA_JOBS_RUNNING, and are created by the script catjobq.sql. This script is also located in the built−in packages source code directory and is automatically run by catproc.sql. Finally, the job queue must have its dedicated background processes started in order to operate properly. This is accomplished by setting an initialization parameter in the INIT.ORA file for the database. The parameter is, JOB_QUEUE_PROCESSES = n where n is a number between 1 and 36. Other INIT.ORA parameters that affect job queue behavior are discussed in the Section 13.2, "Job Queue Architecture"" section. 13.1.1 DBMS_JOB Programs Table 13.1 lists the programs defined for the DBMS_JOB packages. Table 13.1: DBMS_JOB Programs Name Description Use in SQL? 13. Job Scheduling in the Database 574 BROKEN Marks the job as broken; do not re−execute No CHANGE Changes job parameters that can be set by user No CHECK_PRIVS Unknown No INTERVAL Changes execution interval for job No ISUBMIT Submits a new job specifying job number No NEXT_DATE Changes next execution date for job No REMOVE Removes existing job from the queue No RUN Runs the job immediately in current session No SUBMIT Submits a new job obtaining new job number No USER_EXPORT Creates text of call to recreate a job No WHAT Changes PL/SQL executed for job No The DBMS_JOB package does not declare any package exceptions or nonprogram elements. In addition, none of the programs in this package asserts a purity level with the RESTRICT_REFERENCES pragma. 13.1.2 Job Definition Parameters The programs in DBMS_JOB share a set of parameters that define jobs, their execution times, and frequency of execution. All of the DBMS_JOB procedures manipulate one or more of these parameters: Parameter Description job Unique identifier of the job what PL/SQL code to execute as a job next_date Next execution date of the job interval Date function to compute next execution date of job broken Flags job as broken and not to be executed The following sections describe the characteristics of these parameters that apply to all of the procedures that contain them as formal parameters. 13.1.2.1 The job parameter The job parameter is an integer that uniquely identifies the job. It can be either selected by the user or automatically assigned by the system, depending on which of the two job submission procedures is used to enter the job into the job queue. The DBMS_JOB.SUBMIT procedure automatically assigns the job number by obtaining the next value from the sequence SYS.JOBSEQ. It is returned as an OUT parameter so the caller can subsequently identify the job submitted. DBMS_JOB.ISUBMIT allows the user to assign a specific integer identifier to the job, and it is up to the caller to ensure that this number is unique. Job numbers cannot be changed other than by removing and resubmitting the job. The job number is retained even when the database is exported and imported. Be aware of the potential for job number conflicts when performing export/import between databases that contain jobs. 13.1.2.2 The what parameter The what parameter is a character string that evaluates to a valid PL/SQL call to be executed automatically by the job queue. You must enclose the what parameter in single quotes if you are using a string literal. Alternatively, you can use a VARCHAR2 variable containing the desired string value. The actual PL/SQL call must be terminated with a semicolon. To embed literal strings in the PL/SQL call, include two single [Appendix A] What's on the Companion Disk? 13.1.2 Job Definition Parameters 575 . DBMS_JOB DBMS_JOB Examples The DBMS_JOB package is actually an API into an Oracle subsystem known as the job queue. The Oracle job queue allows for the scheduling and execution of PL/SQL routines. the Oracle job queue. DBMS_JOB is used to schedule many different types of tasks that can be performed in PL/SQL and that require regular execution. The job queue is used extensively by Oracle. Started with DBMS_ JOB The DBMS_JOB package is created when the Oracle database is installed. The dbmsjob.sql script (found in the built−in packages source code directory, as described in Chapter