An Oracle blog – Amardeep Sidhu

September 18, 2009

wrap’ed code and SQL trace

Filed under: PL/SQL — Sidhu @ 9:42 pm
Tags: ,

Yesterday, one of my colleagueย asked that if he traced a wrap’ed PL/SQL procedure, would the SQL statements show up in the trace ? Very simple thing but at that moment i got, sort of into doubt. So i ran a simple test and yes they do show up ๐Ÿ˜‰

v_today   DATE;
INTO v_today

C:\>wrap iname=wrap1.sql

PL/SQL Wrapper: Release Production on Fri Sep 18 21:07:49 2009

Copyright (c) 1993, 2004, Oracle.  All rights reserved.

Processing wrap1.sql to wrap1.plb

C:\>more wrap1.plb
65 96


And here is the output from the trace file, showing the SQL statement:

BEGIN wrap1; END;

call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
Parse        1      0.00       0.00          0          0          0           0
Execute      1      0.03       0.01          0          0          0           1
Fetch        0      0.00       0.00          0          0          0           0
------- ------  -------- ---------- ---------- ---------- ----------  ----------
total        2      0.03       0.02          0          0          0           1

Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 54


June 19, 2009


Filed under: PL/SQL,Troubleshooting — Sidhu @ 11:42 pm
Tags: , , ,

Today one of my colleague was working on development of a screen in Oracle Forms to give the end user an option to schedule a job using dbms_scheduler. With the hope that i would be able to explain it properly, the whole scenario is like this:

  1. User will log in to the application with his username (Lets say USER01) and password (basically every application user is a database user).
  2. He is provided with a screen where he can enter details about the job and the code behind the button calls a PL/SQL procedure in the main application schema (lets say APP1) which in turn uses DBMS_SCHEDULER.CREATE_JOB to schedule the new job.
  3. The ultimate task of the job is to move data from one table in the first database to a table in the second database using a DB Link.
  4. There is a VPD policy applied on all the application users to restrict the view of data. Policy function uses SYS_CONTEXT to fetch some information about the logged in user. The main application user APP1 is exempted from policy and can see the whole data.

Things seem to work fine till the schedule part. But when the job runs it hits ORA-02070: database does not support operator SYS_CONTEXT in this context as SYS_CONTEXT and DB link doesn’t go together.

I did a bit of troubleshooting and came to know that the job gets created with JOB_CREATOR (a field in DBA_SCHEDULER_JOBS) as the user who is logged in (ie USER001). Now when the job runs from USER001, there is a VPD policy which is going to append a where clause to the query and there is a DB link being used, hence ORA-02070.

So the way out would be to schedule and run the job from some user that has no VPD policy applied to it. The best choice would obviously be the main application user; APP1 but as the user logs in with his own username so the job would always be created with JOB_CREATOR as USER001. After a bit of thought provoking an idea hit me:

Create a table in the APP1 schema. Now when the user schedules the job, insert the values of the parameters required to schedule the job in the table. Schedule one master job in APP1 schema which would read this table and in turn call DBMS_SCHEDULER.CREATE_JOB to schedule the job required by the user. Now as there is no policy applied on the APP1 database user so the job is not going to hit ORA-02070. The frequency of the master job can be set as per the requirements. To identify which entries in the table have been processed either keep a flag which can be updated or delete the record from the table after scheduling.

That is how it clicked in my mind at that time. Suggestions about any other better (or worse ๐Ÿ˜‰ ) methods are welcome ๐Ÿ™‚

PS: About the title: Nothing really was coming into my mind so i picked up the all three words and titled it DBMS_SCHEDULER, DBMS_RLS and SYS_CONTEXT ๐Ÿ™‚

March 4, 2008

Autonomous Transactions in Oracle

Filed under: PL/SQL — Sidhu @ 8:33 pm

I came across a very nice post about Autonomous Transactions in Oracle written by Kevin Meade on orafaq. Thought about sharing the link.

His blog also has some very nice stuff.

March 3, 2008

Missing grants

Filed under: PL/SQL,SQL,Troubleshooting — Sidhu @ 8:37 pm
Tags: , ,

Today one of my colleague was working on a simple PL/SQL procedure. Based on some logic it was returning count(*) from all_tab_columns for few tables. It gave count incorrectly for one table out of around fifty in total. He just hard coded the table name and ran it but again it showed count as zero.

Then he took the code out of procedure and wrote it in DECLARE, BEGIN, END and after running it showed the correct count. But ran as database procedure it always shows incorrectly.

Finally just as hit and trial, he gave SELECT on the TABLE to database user [Table was in different schema], used to run the procedure and everything was ok. Isn’t it bit stupid ๐Ÿ™‚

Update: Well, it happens for a reason. Nigel Thomas pointed out in the comment. The reason is that privileges granted to a role are not seen from PL/SQL stored procedures. You need to give direct grant to the user for this or another method is to define the procedure or package with invoker rights.

Thanks Nigel ๐Ÿ™‚

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