Oracle and more – Amardeep Sidhu

Today i was refreshing a MVIEW (Oracle 9.2.0.1.0 on Windows 2000) and instead of writing

exec dbms_mview.refresh('SCHEMA1.MVIEW1','C'); 

i wrote

exec dbms_mview.refresh('SCHEMA1','MVIEW1','C');

And it gave me:

ERROR at line 1:
ORA-30019: Illegal rollback Segment operation in Automatic Undo mode
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 794
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 851
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 832
ORA-06512: at line 1

which has nothing to do with the real error. Take care !

Today i was gathering stats on one schema (10.2.0.3 on AIX 5.3, 64 bit) and it said:

ERROR at line 1:
ORA-03001: unimplemented feature
ORA-06512: at "SYS.DBMS_STATS", line 13336
ORA-06512: at "SYS.DBMS_STATS", line 13682
ORA-06512: at "SYS.DBMS_STATS", line 13760
ORA-06512: at "SYS.DBMS_STATS", line 13719
ORA-06512: at line 1

Little bit of searching on Metalink revealed that i had hit Bug no 6011068 which points to the base Bug 576661 which is related to function based indexes. There were 2 function based indexes in the schema. Before talking about the workaround let us re-produce the test case. Here i am doing it on my laptop (10.2.0.1 on Windows XP 32 bit)

SCOTT@TESTING >create table test1 as select * from emp;

Table created.

SCOTT@TESTING >create index ind1 on test1(comm,1);

Index created.

SCOTT@TESTING >

SYSTEM@TESTING>exec dbms_stats.gather_schema_stats('SCOTT');
BEGIN dbms_stats.gather_schema_stats('SCOTT'); END;

*
ERROR at line 1:
ORA-03001: unimplemented feature
ORA-06512: at "SYS.DBMS_STATS", line 13210
ORA-06512: at "SYS.DBMS_STATS", line 13556
ORA-06512: at "SYS.DBMS_STATS", line 13634
ORA-06512: at "SYS.DBMS_STATS", line 13593
ORA-06512: at line 1

SYSTEM@TESTING>

As suggested in the metalink article let us set event 3001 before running the GATHER_SCHEMA_STATS command.

SYSTEM@TESTING >alter session set tracefile_identifier=stats1;

Session altered.

SYSTEM@TESTING >alter session set events '3001 trace name ERRORSTACK level 3';

Session altered.

SYSTEM@TESTING >exec dbms_stats.gather_schema_stats('SCOTT');
BEGIN dbms_stats.gather_schema_stats('SCOTT'); END;

*
ERROR at line 1:
ORA-03001: unimplemented feature
ORA-06512: at "SYS.DBMS_STATS", line 13210
ORA-06512: at "SYS.DBMS_STATS", line 13556
ORA-06512: at "SYS.DBMS_STATS", line 13634
ORA-06512: at "SYS.DBMS_STATS", line 13593
ORA-06512: at line 1

SYSTEM@TESTING >

Part of the trace file reads:

ksedmp: internal or fatal error
ORA-03001: unimplemented feature
Current SQL statement for this session:
select /*+ no_parallel_index(t,IND1) dbms_stats cursor_sharing_exact use_weak_name_resl dynamic_sampling(0) no_monitoring no_expand index(t,"IND1") */ count(*) as nrw,count(distinct sys_op_lbid(51966,'L',t.rowid)) as nlb,count(distinct hextoraw(sys_op_descend("COMM")||sys_op_descend(1))) as ndk,sys_op_countchg(substrb(t.rowid,1,15),1) as clf from "SCOTT"."TEST1" t where "COMM" is not null or 1 is not null
----- PL/SQL Call Stack -----
object      line  object
handle    number  name
65AA77D4      9406  package body SYS.DBMS_STATS
65AA77D4      9919  package body SYS.DBMS_STATS

So the problem is being caused by the index ind1 we created on (comm,1). This bug has been fixed in 10.2.0.5 and 11.1.0.7. The available workaround for other versions is to create index using 1 as character instead of number.

SCOTT@TESTING >drop index ind1;

Index dropped.

SCOTT@TESTING >create index ind1 on test1(comm,'1');

Index created.

SCOTT@TESTING >

And now running GATHER_SCHEMA_STATS:

SYSTEM@TESTING >exec dbms_stats.gather_schema_stats('SCOTT');

PL/SQL procedure successfully completed.

SYSTEM@TESTING >

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 ) methods are welcome

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

Since long time i have almost been writing useless posts only. Now, i guess my blog doesn’t even look like an Oracle blog. So thought about posting something related to Oracle

Day before yesterday a colleague at my workplace asked that she was running an SQL script (which contained a simple DBMS_MVIEW.REFRESH() statement to refresh an MVIEW), it ran successfully but after completion re-ran the last command run in the session. I was also puzzled and checked the SQL script but it contained simple DBMS_MVIEW.REFRESH() statement. Next try revealed that the script actually had a / (slash) in the second line (with no semi-colon at the end of the first line). Something like this (I used dbms_stats instead of dbms_mview):

exec dbms_stats.gather_table_stats(user,'EMP')
/

Now this thing, when run in SQL* Plus session can be confusing:

SCOTT@TESTING >
SCOTT@TESTING >delete emp1;
delete emp1
*
ERROR at line 1:
ORA-00942: table or view does not exist

SCOTT@TESTING >@c:\test

PL/SQL procedure successfully completed.

delete emp1
*
ERROR at line 1:
ORA-00942: table or view does not exist

SCOTT@TESTING >

There is no semicolon at the end of the first statement but it executes without that also. So the slash in the 2nd line simply re-executes the last SQL, as expected . But it does get confusing !

Today I was upgrading 10gR1 to 10gR2 (10.2.0.1) on Linux x86. The upgrade went almost fine (except that I had to install one package and change few kernel parameters) but while running DBUA to upgrade databases, it gave an error:

Could not get database version from the Oracle Server component. The CEP file rdbmsup.sql does not provide the version directive

and

Start of root element expected. Upgrade Configuration file
'C:\Oracle10g2\cfgtoollogs\dbua\test\upgrade5\upgrade.xml' is not a valid XML file.

I searched in the metalink and found that this all happens due to customized glogin.sql file which was there in my case also. And removing that customization made DBUA rock

You might want to check here, here and here.