Oracle PL/SQL - tips for immediate output / console printing

Question

I have a number of pl/sql procedures that can take several minutes to run. While developing them, I've added a few print statements to help debug and also provide some feedback and progress indicators. Initially, I ran these on small test sets and output was almost instantaneous. Now that I'm testing with larger test sets that take several minutes to run, I find that printing to the console is no longer suitable, because nothing gets printed until the procedure ends. I'm used to working in environments that do not buffer their output and print it immediately and adding simple print-statements for simple debugging and diagnostic is common.

Is it possible in pl/sql to print output immediately (not buffered)? If not, what alternatives do people recommend to get a similar result?

Answer 1

You can have a procedure that writes messages to a table using an autonomous transaction something like:

procedure log (p_message)
is
    pragma autonomous_transaction;
begin
    insert into message_log (user, datetime, message)
    values (user, sysdate, p_message);
    commit;
end;

Then monitor the table from another Oracle session.

Answer 2

we have a small trick for this.

you can use DBMS_APPLICATION_INFO.set_client_info(" some information here"); creating some variables and replace the string inside " ".

and use select client_info from v$session to monitor the progress.

Answer 3

I've been using dbms_pipe for this purpose. Send messages to a named pipe and read them from another session. This method may not work in a RAC environment when the writing and reading processes may connect to a different node.

Alternatively you can insert messages into a table using a procedure that runs in its own session using "pragma autonomous_transaction". You can the query these messages from another session

Edit: I see that my second option has already been mentioned.

Answer 4

There are generally two options:

• Send the output to an Oracle table (or temporary table)
• Write to the (database host) filesystem with UTL_FILE

If you don't have OS access to the database host, you can still write to the dbhost filesystem and bind an Oracle externally-defined table to the file so it can be queried with a SELECT.

Answer 5

It may depend on your client tool. I haven't used SQL*Plus in a while, but when I'm debugging procedures in PL/SQL Developer, I open a command window and issue a SET SERVEROUTPUT ON command. Then when I execute the procedure, anything printed by DBMS_OUTPUT.PUT_LINE shows up right away.

Edit: you're right, I guess I was only seeing that with larger amounts of output or something. Anyhow I did some searching online and came across this log4plsql - may be useful.

Answer 6

An alternative is to use a pipelined function that returns your logging information. See here for an example: http://berxblog.blogspot.com/2009/01/pipelined-function-vs-dbmsoutput.html When you use a pipelined function you don't have to use another SQLPLUS/Toad/sql developer etc... session.

Answer 7

You can use DBMS Pipe and the Pipe Viewer in PL/SQL Developer to asynchronously catch all infos as they are put into the pipe.

Be careful to only put things into a pipe when there's someone to read it. Otherwise, your call will fail when the pipe is full.

There's also the possibility of using events, PL/SQL Developer has an event monitor as well. And the docs should provide an example of how to do it.

Answer 8

Another option is to have your PL/SQL call a procedure to send an email with the log message in it. This requires that your database has email sending capability, which can be added using UTL_SMTP.