Oracle Scheduling Running OS Commands and Scripts from PL/SQL

Running OS Commands and Scripts from PL/SQL

Not all jobs that can be scheduled are written as stored procedures.  Sometimes it is necessary to schedule jobs to run operating system commands or batch scripts.  Typically, these types of jobs have been scheduled using an operating system scheduler, such as CRON, since it is not possible to call operating system command or executable scripts natively from PL/SQL.  Splitting job scheduling between two schedulers can get confusing, so many database administrators resign themselves to only using the operating system scheduler.

The scheduler in Oracle10g can be used to schedule operating system commands and scripts natively, giving the option of avoiding the operating system scheduler.  This is great if using Oracle10g, but what can be done if using Oracle 8i and 9i?  One method is to use Java stored procedures to do the work.

First, the Java stored procedure that will actually do the work needs to be created.

* Host.java

-- -- Parameters:
--    1) Host command or executable file to execute.
-- *****************************************************************

CREATE OR REPLACE AND COMPILE JAVA SOURCE NAMED "Host" AS
import java.io.*;
public class Host {
  public static void executeCommand(String command) {
    try {
      String[] finalCommand;
      if (isWindows()) {
        finalCommand = new String[4];
        finalCommand[0] = "C:\\winnt\\system32\\cmd.exe";
        finalCommand[1] = "/y";
        finalCommand[2] = "/c";
        finalCommand[3] = command;
      }
      else {
        finalCommand = new String[3];
        finalCommand[0] = "/bin/sh";
        finalCommand[1] = "-c";
        finalCommand[2] = command;
      }

        final Process pr = Runtime.getRuntime().exec(finalCommand);
      new Thread(new Runnable() {
        public void run() {
          try {
            BufferedReader br_in = new BufferedReader(new
InputStreamReader(pr.getInputStream()));
            String buff = null;
            while ((buff = br_in.readLine()) != null) {
              System.out.println(buff);
              try {Thread.sleep(100); } catch(Exception e) {}
            }
            br_in.close();
          }
          catch (IOException ioe) {
            System.out.println("Exception caught printing process output.");
            ioe.printStackTrace();
          }
        }
      }).start(); 

      new Thread(new Runnable() {
        public void run() {
          try {
            BufferedReader br_err = new BufferedReader(new
InputStreamReader(pr.getErrorStream()));
            String buff = null;
            while ((buff = br_err.readLine()) != null) {
              System.out.println(buff);
              try {Thread.sleep(100); } catch(Exception e) {}
            }
            br_err.close();
          }
          catch (IOException ioe) {
            System.out.println("Exception caught printing process error.");
            ioe.printStackTrace();
          }
        }
      }).start();
    }
    catch (Exception ex) {
      System.out.println(ex.getLocalizedMessage());
    }
  }
 
  public static boolean isWindows() {
    if (System.getProperty("os.name").toLowerCase().indexOf("windows") != -1)
      return true;
    else
      return false;
  }

};
/

show errors java source "Host"

The Host.java procedure is loaded in the same way as a PL/SQL stored procedure.

In order to call the Java stored procedure, a PL/SQL call specification must be published.  This is essentially a PL/SQL wrapper with the correct parameter list which allows the Java code to be called as if it were a PL/SQL procedure or function.

By default, the JServer has very little access to the operating system of the database server.  To make sure there are no problems accessing the file system and operating system commands, the appropriate permissions using the grant_permission procedure of the dbms_java package must be given to the user.

Assuming that job_user is the schema that owns the Host Java stored procedure, the following permissions need to be granted:

The effects of these permissions are only seen when the grantee reconnects.

The host_command procedure can be tested as follows:

With the host_command procedure in place, the OS commands can now be scheduled using the dbms_job package the same way any normal PL/SQL procedure is used.

Care should be taken over who gets access to the host_command procedure as it runs OS commands and executable scripts as the operating system user that owns the Oracle software.  As such, it can be the cause of security vulnerabilities if used incorrectly.

This is an excerpt from the book "Oracle Job Scheduling" by Dr. Tim Hall. You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle job scheduling scripts.