DBMS_OUTPUT is a technology that many Oracle people will just assume you already grok. It is a very basic building block for Oracle PLSQL programs. If you do not understand it, then your first attempts at scripting will likely be very frustrating.

So in a nutshell from the Oracle Docs

The DBMS_OUTPUT package enables you to send messages from stored procedures, packages, and triggers. The package is especially useful for displaying PL/SQL debugging information.

DBMS_OUTPUT provides a method of communication for for your program.

Did you hear something?

So this post is going to be pretty boring if you’ve worked with Oracle for more than a few months. But, feel free to skip ahead to see how to activate the output support in SQL Developer.

What is DBMS_?

DBMS is short for Database Management System. You have have heard of a RDBMS? Oracle is an example of an RDBMS. Part of Oracle’s ‘management system’ is a collection of support packages. A majority of these packages are owned by the ‘SYS’ user, and are prefixed by ‘DBMS_’.

Don’t have access to the SYS schema? That’s OK, there is a PUBLIC SYNONYM for SYS.DBMS_OUTPUT called ‘DBMS_OUTPUT.’ That’s why you’ll see it called in your code as

  DBMS_OUTPUT.PUT_LINE(''); -- like so

It’s also granted to PUBLIC. That means everyone can see it, AND everyone can use it.

So How does it work?

You want to write something. That would be the PUT_LINE() procedure. But where does it go? According to the package spec, the message is written ‘in the buffer.’ Think of this as a memory space. You write to it, and you can read from it. So you make a call to write (PUT_LINE), and then you make a call to read (GET_LINE.)

What most new folks don’t realize is that

Messages sent using DBMS_OUTPUT are not actually sent until the sending subprogram or trigger completes. There is no mechanism to flush output during the execution of a procedure.

This means you cannot read the messages as the program executes. Everything gets written to the buffer at once, after the program has completed.

All of this is generally handled by your IDE. Most developers will use DBMS_OUTPUT for debugging purposes. No one is going to read these messages but the developer (most likely.) Need something more poweful and flexible? You can also write to a file or even to the web.

Using DBMS_OUTPUT in SQL Developer

In the worksheet or in the Procedure Editor, you will write your code. Here is a simple anonymous PLSQL block

 DBMS_OUTPUT.put_line('Are you there Codd, it''s me, Jeff.');

Step 0: Enable DBMS_OUTPUT
This is step 0 because most folks will start with step 1, and forget this step and have to start all over.

View – Dbms Output

With the DBMS_OUTPUT panel open, click the ‘Enable’ button.

Turn it on!

Step One: Run the code.
Use the ‘Run Script’ toolbar, or it’s keyboard shortcut, F5.

Step Two: Check the output panel.
You will notice the output shows up almost immediately after the ‘completed’ message appears in the regular ‘Script Output’ panel.

One last thing, mind the buffer size.

Remember that buffer thing we’re writing to with the package? You only get so much space. The default is 20,000 which equates to about 20,000 characters in most systems. You can increase it to 1,000,000, or my favorite – UNLIMITED.

See Tom’s take on “ORA-20000: ORU-10027: buffer overflow, limit of 10000 bytes.”

SQL Developer’s DBMS_OUTPUT panel allows you to set the buffer size directly. We also handle the GET and ENABLE calls – stuff that you should expect from your PLSQL IDE. Once you understand how it works, it’s very easy. If you’re a n00b though, I can see why you might have been confused and frustrated (until now of course!)

Unlimited isn't free!

Mind the buffer size. You’ll be consuming memory, and the more you ask for, the more likely you are to attract the attention of the DBAs.


I'm a Distinguished Product Manager at Oracle. My mission is to help you and your company be more efficient with our database tools.


  1. Hi Jeff, great post as always!

    Quick question here. Somehow my DBMS_OUTPUT window (along with ‘messages’ tab) ended up as a separate window to the main one… It’s no longer a section below (or to the side of) it, but is a separate free-floating window elsewhere on the desktop.

    How do I push it back into the main window? Nothing I tried works. Quitting and restarting SQLDev didn’t work either… (on a Mac in case it matters, but assuming it wouldn’t)

    Many thanks in advance!

    • Windows > Reset to factory settings

      Or right click on the floating panel (DBMS_OUTPUT) and say ‘Dock’

    • Jeff, You are a LIFESAVER is always!
      Right click: no luck at all, possibly a Mac thing. Reset did the trick though.
      I owe ya one 🙂

  2. Hello Jeff:

    I am a T-SQL developer, but new to PL/SQL and SQL server developer. I downloaded and installed sqldeveloper- I write two stored procedures to learn sqldeveloper and PL/SQL. They are executed successful, but I see nothing in SQL developer. I don’t know whether this is a preference set up issue or my PL/SQL issue.

    1. Hello world stored procedure

    dbms_output.put_line(‘Hello World!’);

    EXECUTE greetings;

    2. Stored Procedure to show a table data in Oracle sample database table.

    PROCEDURE pr_print_result(
    p_result OUT sys_refcursor)
    END ;
    –var sys_refcursor p_result;
    EXECUTE pr_print_result(p_result=>:p_result);
    — Want to see the data in OT.CONTACTS, but nothing shows


    Thank you in advance,


  3. Mark Wright Reply

    So that 1M limit on dbms output seems to only be in sql developer which Is my favorite tool for scirpt/update deployment any way around that? I can run beyond 1M in other products or even sqlplus.

    • Mark Wright

      If i set it to unlimited or dbms_output.enable(null) same result. chokes on 1m characters.

    • Mark Wright

      Update. I’ve tried to recreate the problem without using the script that was submitted for code push and I was able to pass 1m characters just fine, so now it’s back to the organic code to see what the problem is.

  4. Hi Jeff,
    Ran into an interesting issue: have an anonymous block with a cursor and definition and a body that pretty much loops for every record and does dbms_output.put_line. Before the first line of output is printed, we’re seeing two ‘1’s, one per line. Sometimes it’s 4 lines (with one ‘1’ on each, sometimes it’s 6). Running the cursor on its own and showing its results is fine (no 1s), as is a trivial sample proc of printing dummy output. The buffer is set for 200,000 but the output is nowhere near. Do you know what might be causing this behaviour?
    Thank you!

    • Not really, it’s triple digits for the lines of code in the query and trying to dummy it down isn’t meaningful. Thought perhaps you’d encountered this before and have a starter pointer to a root cause… Those ‘1’ rows are only seen in dbms_output and aren’t returned in the result set in the worksheet…

    • we’re theoretically getting all that data from the buffer. Here’s the code we run to get that for you

          l_line varchar2(32767);
          l_done NUMBER;
          l_buffer varchar2(32767) := '';
          l_lengthbuffer NUMBER := 0;
          l_lengthline NUMBER := 0;
          dbms_output.get_line( l_line, l_done ); 
          IF (l_buffer IS NULL) THEN 
            l_lengthbuffer := 0; 
            l_lengthbuffer := LENGTH(l_buffer); 
          END IF; 
          IF (l_line IS NULL) THEN 
            l_lengthline := 0; 
            l_lengthline := LENGTH(l_line); 
          END IF; 
        exit WHEN l_lengthbuffer + l_lengthline > :maxbytes OR l_lengthbuffer + l_lengthline > 32767 OR l_done = 1; 
        l_buffer := l_buffer || l_line || chr(10); 
          END loop; 
          :done := l_done; 
          :buffer := l_buffer; 
          :line := l_line; 
  5. In SQL cmd prompt after creating the basic procedure when we run it with “exec procedure_name” getting the output as “PL/SQL procedure successfully completed” not displaying the message given inside.

    • That’s a problem with your PL/SQL then – you have to code it to print any message. And if you’re using DBMS_OUTPUT for that, you have to enable serveroutput for your Oracle session, SQLcl or SQL Developer or SQL*Plus

  6. This works on multiple instances, but does nothing on any instances here.
    I’m using SQL Developer

    My DBMS output window is connected to the same instance as my worksheet query window.
    I’ve set serveroutput on (both in a startup script, and in the session).
    I’ve restarted sql developer.
    Executing any of your sample scripts produces a: “PL/SQL procedure successfully completed.” in the script output window, but nothing in the dbms_output window.
    Another developer here tried getting this to work as well, and couldn’t.
    Something as simple as: `exec dbms_output.put_line(‘test’);` produces nothing .

    Can you think of any other server settings that would possibly prevent this from working (on our Oracle 10 instances)?


  7. Hi,
    I’m using version
    I have a very simple stored procedure
    create or replace PROCEDURE PR10_2_B AS
    END PR10_2_B;

    If I click right button /Run the procedure a new tab ‘Running…..log’ is created and I can see the output….. in almost all my pc… In some of them I can’t see the output.

    Then I have enabled dbms_output window and then if I execute the procedure from a worksheet with something like

    I can see the output in the “script output” tab and in the dbms_output tab….This works in all the pc……

    Why I cant´t see the dbms output in the ‘Running……log’ tab in all the computers? Should I configure something?

    Thank you,

    • Hello,
      I have executed set serveroutput on and is the same…. in most computers it works perfect (without serveroutput on even), but in some of them it doesn’t work…. I can see the output in the “script output” tab and in the dbms_output tab only, not in the “Running….log” tab…


  8. I am creating a text file using oracle unnamed function where in I am using dbms_ouput.put_line. every thing is going well except one blank line is created in last, I do not want that blank line.
    It will be great of any one may like to help me? I am using following setting. using Oracle 11 DB

    • Preguntón Cojonero Cabróncete

      I use PL SQL Developer. HOw use dDBMS_OUTPUT to log in a file ?

    • Client side or database side?

      Write code, poll for dbms output, use utl_file to write it to a file on the server

      If you mean client-side via PL/SQL Developer – you should ask them. I do SQL Developer, it’s a completely different product.

  9. Jeff,
    I just installed 4.1 and it works very differently from 3-2. in 3-2 dbms_outputs went in line with the connection run of a sql package procedure
    with 4.1 I followed your instructions to get a separate dbms_output window and I was still not getting any outputs displayed from my packaged procedure until I added in my procedure code DBMS_OUTPUT.ENABLE;
    it took me a good frustrating time to figure that cause the DBMS_OUTPUT window was displaying output from my sql session but not from my plsql package

  10. Is there a way to clear the DBMS Output window other than clicking the ‘Clear’ option. Im looking for a code to add to an existing script which clears the dbms ouput everytime i run it.

    • Thanks!. But Im using DBMS_OUPUT.PUT_LINE to print some of the results in the script. So my output will be in DBMS Output window only. Any suggestions to clear this window?

    • >>So my output will be in DBMS Output window only
      not true

      SET SERVEROUTPUT ON -> will throw dbms output to the script output

  11. I was just playing around with this and got into a situation where SQL Developer Script Output and DBMS Output (which is actually Dbms Output in the UI… That should probably be fixed at some point…) were not showing anything at all. SQL Developer had been open forever including some disconnects of the VPN software needed to get to the database. I tried to reset my connection with a reconnect within SQL Developer, but ultimately it required a complete restart of SQL Developer for my Script Output and DBMS Output to actually show anything.

    Just and FYI.


    • Anand,

      See my comment below. If you’ve followed everything in the post, it might be that you have to restart SQL Developer.


  12. Hi, bro 🙂 Thanks for this article. Can I ask you something? I’m wondering how to output record variable: DBMS_OUTPUT.PUT_LINE(vr) is wrong. My “vr” variable contains 3 fields I assigned with SELECT statement with no errors. Thanks for help 🙂

    • Kamil,

      If you post your code we could take a look at it.

      The below works:

      l_test_value VARCHAR2(2000) := ‘This is some value’;
      l_output varchar2(2000);
      SELECT l_test_value INTO l_output FROM dual;

  13. Rusty Bullerman Reply

    I am trying to generate a report in csv using SQLDeveloper. The report generates approximately 1.7 MB of output. I set the buffer size to unlimited and run the report. I get the following error message:

    Error report:
    ORA-20000: ORU-10027: buffer overflow, limit of 1000000 bytes
    ORA-06512: at “SYS.DBMS_OUTPUT”, line 32
    ORA-06512: at “SYS.DBMS_OUTPUT”, line 97
    ORA-06512: at “SYS.DBMS_OUTPUT”, line 112
    ORA-06512: at line 1031
    20000. 00000 – “%s”
    *Cause: The stored procedure ‘raise_application_error’
    was called which causes this error to be generated.
    *Action: Correct the problem as described in the error message or contact
    the application administrator or DBA for more information.

    Is unlimited 1000000 bytes?

    • No, but this will do it

      Or use the /*csv*/ script trick and we’ll generate the csv for you, then spool it to a file instead of using dbms_output

    • I had a similar problem with SQL DEVELOPER Version Build 15.21
      After I had changed my first script line from SET SERVEROUTPUT ON to SET SERVEROUTPUT ON SIZE UNLIMITED (had also tried adding DBMS_OUTPUT.ENABLE(2000000) with no effect), the same error still occurring:
      Error report –
      ORA-20000: ORU-10027: buffer overflow, limit of 1000000 bytes
      ORA-06512: at “SYS.DBMS_OUTPUT”, line 32
      ORA-06512: at “SYS.DBMS_OUTPUT”, line 97
      ORA-06512: at “SYS.DBMS_OUTPUT”, line 112
      ORA-06512: at line 104
      20000. 00000 – “%s”
      *Cause: The stored procedure ‘raise_application_error’
      was called which causes this error to be generated.
      *Action: Correct the problem as described in the error message or contact
      the application administrator or DBA for more information.

    • if you try to print more than what will fit in the buffer, you’ll get that error message

    • What do you mean here? What buffer and where do you setup this?
      I believed setting “unilimited” should allow all possible output on script output window.

    • Hmm not quite sure, but problem fixed with:

      😉 Thanks!

  14. Is there a way to see DBMS_OUTPUT when I’m running a stored proc using the “RUN” command from the menu?

    • Yes, we show that in the ‘Running … – Log’ panel you see at the bottom of the SQL Devleoper desktop, between Messages and Output Variables.

      You can also open the DBMS_OUTPUT panel, available under the View menu, and enable polling for that connection. This will show JUST the DBMS_OUTPUT for that connection.

  15. Straight forward, simple, and to the point! Thank you very much for this. The quick and easy answer I was looking for. As you stated yourself in Step 0, I always skipped to Step 1 without even realizing that’s what I was doing. lol, all I was missing was enabling the function in SQL Developer.

    Thank you!

  16. Jackie F. Oram Reply

    I am new to PL/SQL. I currently have a block that contains three update statements. Each ends in a dbms_output.put_line(SQL%ROWCOUNT) and then a commit. The first is for summer processing. The second is for fall processing. The third is for spring processing. Only the summer and spring updates are outputted by the dbms.

    Please tell my why this is.

    Thank you!

    • No idea, I’d have to see your code.

      Is there a conditional block in there? Maybe your fall processing code isn’t actually being executed.

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