Oracle New Visual Online Tools

Hi all,
So, after a long time of same old documentation style, Oracle started sharing some nice and visual pages for some specifics. Here are 2 examples:

1. Oracle Move to Cloud  (http://www.oracle.com/goto/move)
This one was shown to me by Ricardo Gonzalez, and it’s a GREAT tool if you are planning migrations to Oracle Cloud in general.

The part I like most is where you select the source and destination formats/versions you want and all recommended migration methods are suggested. Of course additional validation on database are required for each method, but it can potentially remind you of things you may be forgetting.

NewScreenshot 2019-05-08 às 16.56.46

Something else I like very much as well is the section with executive summaries of each migration tool. It’s basically ready for a print screen to put in the slides you are going to present to your boss… 🙂

NewScreenshot 2019-05-08 às 16.57.16.png

Also, you have handy some links to papers for the most different migration scenarios, as per:

NewScreenshot 2019-05-08 às 16.57.24

2. Oracle Database Features: (https://apex.oracle.com/database-features/)
I actually got it from this post by Portilho, and found it great! See how it looks like:

NewScreenshot 2019-05-08 às 16.52.14

And by selecting any of the features you can see more info in a very simple way, as per below. By the way, with one click you can be directed to the documentation (the old fashioned one):

NewScreenshot 2019-05-08 às 16.55.08

 

Hope you enjoy those as much as I did and hope Oracle continue providing those sort of interfaces to us!

Cheers!

AWR Scripts List

Hey,
You also always need to lookup for the right AWR Script to run, just like me?

Here is a quick summary that may help you (and myself) in future. 🙂

@?/rdbms/admin/awrrpt.sql      --> basic AWR report
@?/rdbms/admin/awrsqrpt.sql    --> Standard SQL statement Report
@?/rdbms/admin/awrddrpt.sql    --> Period diff on current instance
@?/rdbms/admin/awrrpti.sql     --> Workload Repository Report Instance (RAC)
@?/rdbms/admin/awrgrpt.sql     --> AWR Global Report (RAC)
@?/rdbms/admin/awrgdrpt.sql    --> AWR Global Diff Report (RAC)
@?/rdbms/admin/awrinfo.sql     --> Script to output general AWR information

Hope it helps!
Cheers!

Everything Stopped on ORA-02002!

Hi all,
So, I got contacted by a client in emergency because no more sessions were being opened on database with error ORA-02002. Even worse, everything stopped working and started raising this error.

Unusual, right?

So , checking on this trace generated for error here is what I found:

ORA-02002: error while writing to audit trail
ORA-00604: error occurred at recursive SQL level 1
ORA-01653: unable to extend table SYS.AUD$ by 8 in tablespace AUDIT_TBS

Seems client has moved the AUD$ to another tablespace to avoid filling SYSTEM, just like described in this post. The tablespace got full, however, due bad monitoring, it got full.

As the auditing facility was unable to write to the AUDIT_TRAIL table, SQL statements that were currently being audited also failed.

What to do?

  1. Turn off auditing for the database
  2. Restart database
  3. Add space to tablespace
  4. Re-enable auditing, if required.

To avoid application back and forth, I did it in restrict mode, until get all fixed.

To avoid this sort of issue:

  • Be sure you are monitoring properly the new tablespace.
  • Place the audit tablespace on a reliable disk location and perhaps mirrored for protection.

Hope it helps,
Cheers!

1st GUORS Meetup 2019!

Hi all,
Stay sharp for the first event on GUORS this year!

The event is tacking place next  April 24th, Thursday, at 13h15 in TecnoPUC – Porto Alegre/RS. The topics are:

• Value of Data in Companies – Renato Eric – Oracle
• Implementing #BigData #Analytics #DataScience with Oracle GoldenGate – Maiquel de Oliveira – Sicredi
• Virtualizing Oracle Databases with ACFS/gDBClone – Ricardo Martins – Dell

Subscribe Now! See you there!

12.2 Scheduler Job Disappeared After Creation

Hi all,
Just sharing an experience here. Recently in a migrated 12.2 environment I created a Scheduler Job and it simply disappeared. How come?
Well, seems since 12.2 the AUTO_DROP attribute is set to true by default. I absolutely don’t know why. So I had to recreate the job and set auto_drop to false, simple like this.

I couldn’t find any related bug on MOS, but I’d relate this as a bug, once the default behavior have changed with no prior information.
So, now on, I strongly suggest you to check on your job AUTO_DROP attribute after job creation.

Here is a test case that reproduces the problem:

In a 12.2 database:

begin 
  DBMS_SCHEDULER.create_job (
    job_name        => 'TEST_JOB',
    job_type        => 'PLSQL_BLOCK',
    job_action      => 'BEGIN null; END;',
    start_date      => SYSTIMESTAMP,
    repeat_interval => 'SYSTIMESTAMP + INTERVAL ''10'' SECOND',
    end_date        => NULL,
    enabled         => false,
    comments        => 'Test job');
end;
/
select ENABLED, AUTO_DROP, STATE, RUN_COUNT, FAILURE_COUNT,DEFERRED_DROP from dba_scheduler_jobs where job_name = 'TEST_JOB';
-- Job should appear here

begin 
  dbms_scheduler.enable('TEST_JOB'); 
  dbms_scheduler.run_job('TEST_JOB',false); 
end;
/
 
select ENABLED, AUTO_DROP, STATE, RUN_COUNT, FAILURE_COUNT,DEFERRED_DROP from dba_scheduler_jobs where job_name = 'TEST_JOB';

-- There is no job now in 12.2.

You can take the AUTO_DROP easily from the query above, or using getting the job_ddl and you’ll see the AUTO_DROP set to true, as in the bottom of this page by Tim Hall.

Hope it helps!
Cheers!

ORA-00600 [ipc_recreate_que_2]

Hi all,
So this week I started receiving this error in a client environment. This was happening due Bug 26803191 – Getting ORA-00600 [ipc_recreate_que_2] instead of ORA-27515 – superseded (Doc ID 26803191.8)
In summary, failures due to low memlock limit are leading ORA-00600 [ipc_recreate_que_2] instead of ORA-27515, patching ensure that ORA-27515 is raised on failures due to low memlock limit instead of this ORA-600.

As workaround, the memlock limited can be changed, as also described in MOS ORA-00600: Internal Error Code, Arguments: [ipc_recreate_que_2] When Running Exachk (Doc ID 2480088.1).

Before:

[boesing@exa1dbadm01 trace]$ grep memlock /etc/security/limits.conf |grep oracle
# - memlock - max locked-in-memory address space (KB)
oracle soft memlock 237809520
oracle hard memlock 237809520

After:

[boesing@exa1dbadm01 ~]$ grep memlock /etc/security/limits.conf
# - memlock - max locked-in-memory address space (KB)
oracle soft memlock unlimited
oracle hard memlock unlimited
* soft memlock 32768
* hard memlock 32768

Hope it helps,
Cheers!

ORA-00600: internal error code, arguments: [13011], [7907] on SYS.DBMS_AQ_INV

Hi all,

So a couple weeks ago I was facing the following on a client environment. It was appearing every 10 mins on alert.log:

ORA-00600: internal error code, arguments: [13011], [7907], [12679954], [1], [13461738], [0], [], [], [], [], [], []
ORA-01403: no data found
ORA-06512: at "SYS.DBMS_AQ_INV", line 1248

I could find several references to ORA-600 [13011], always related to some internal corruption. As this table is related to Advanced Queueing, decided to check on Scheduler Job table structures:

SQL> analyze table SYS.SCHEDULER$_EVENT_LOG validate structure cascade; 

Table analyzed. 

SQL> analyze table SYS.SCHEDULER$_JOB_RUN_DETAILS validate structure cascade; 
analyze table SYS.SCHEDULER$_JOB_RUN_DETAILS validate structure cascade 
* 
ERROR at line 1: 
ORA-01499: table/index cross reference failure - see trace file

SQL> analyze table SYS.SCHEDULER$_JOB_RUN_DETAILS validate structure;

Table analyzed.

Ahá!
Also on the generated trace file:

2019-03-01 22:26:37.736 
SESSION ID:(39.32751) 2019-03-01 22:26:37.736 
CLIENT ID) 2019-03-01 22:26:37.736 
SERVICE NAME:(SYS$USERS) 2019-03-01 22:26:37.736 
MODULE NAME:(sqlplus.exe) 2019-03-01 22:26:37.736 
CLIENT DRIVER:(SQL*PLUS) 2019-03-01 22:26:37.736 
ACTION NAME) 2019-03-01 22:26:37.736 
CONTAINER ID:(1) 2019-03-01 22:26:37.736 
Table/Index row count mismatch 
table 273184 : index 275017, 1832 
Index root = tsn: 1 rdba: 0x00c0128a

So ANALYZE on table SCHEDULER$_JOB_RUN_DETAILS fails with CASCADE but succeeds without CASCADE. This means that there is a problem with one of the index of this table. It has gone out of sync with the table.

SQL> select 'alter index '||owner||'.'||index_name||' rebuild;' from dba_indexes where table_name='SCHEDULER$_JOB_RUN_DETAILS';

'ALTERINDEX'||OWNER||'.'||INDEX_NAME||'REBUILD;'
--------------------------------------------------------------------------------
alter index SYS.I_SCHEDULER_JOB_RUN_DETAILS rebuild;

SQL> alter index SYS.I_SCHEDULER_JOB_RUN_DETAILS rebuild online;

Index altered.

After this, error solved and no more recurrence of that ORA-600.

Also note I couldn’t find any document about this on MOS, so this is kind of exclusive by now. 🙂

Cheers!

Restore table statistics using dbms_stats

Hi all, another quick as reference. Table statistics as everyone knows are  very important when the CBO is creating the execution plan. When you have new statistics Oracle will invalid the current execution plans affected by them and create new execution plans based on the new statistics. Most of the time it gets right  if that causes your execution plan to change for worse?

In this situations dba_tab_stats_history   view and dbms_stats.restore_table_stats procedures are your friends.

To validate set and check and set the stats history:

select dbms_stats.get_stats_history_retention from dual; 
exec dbms_stats.alter_stats_history_retention(30);

On dba_tab_stats_history you can view the last statistics available:

select table_name, stats_update_time, from dba_tab_stats_history where table_name='TABLE1' and owner='USER' order by 2 desc;

Use the dbms_stats.restore_table_stats to restore the statistics:

exec dbms_stats.restore_table_stats(ownname=>'USER',tabname=>'TABLE1',AS_OF_TIMESTAMP=>'DATE from column STATS_UPDATE_TIME on dba_tab_stats_history');

Hope it helps!

Elisson Almeida

Oracle 11g Semantic Hints

Hi All!
I was reviewing some features in Oracle and, basically, every single time I review them I find something new. Seems Oracle Databases’ features are near to infinite and we frequently find some that can really add value to our solutions.

Here is a quick summary I did for a client regarding new Semantic Hints on 11g..

11g New Semantic Hints

In Database version 11.2.0.1, Oracle introduced three new hints: IGNORE_ROW_ON_DUPKEY_INDEX, CHANGE_DUPKEY_ERROR_INDEX and RETRY_ON_ROW_CHANGE. They have different working ends but they all tries to avoid ORA-0001 in some specific situations. An important note is that, unlike almost all other hints, this hint has a semantic effect: it changes the actual behavior – not just the optimization – of the SQL. Oracle Docs says about this Hint:

“The CHANGE_DUPKEY_ERROR_INDEX, IGNORE_ROW_ON_DUPKEY_INDEX, and RETRY_ON_ROW_CHANGE hints are unlike other hints in that they have a semantic effect. The general philosophy explained in “Hints” does not apply for these three hints.”

Some specifics about each one:

  • IGNORE_ROW_ON_DUPKEY_INDEX: “When a unique key violation is encountered, a row-level rollback occurs and execution resumes with the next input row.”
  • CHANGE_DUPKEY_ERROR_INDEX: “The CHANGE_DUPKEY_ERROR_INDEX hint provides a mechanism to unambiguously identify a unique key violation for a specified set of columns or for a specified index. When a unique key violation occurs for the specified index, an ORA-38911 error is reported instead of an ORA-001.”
  • RETRY_ON_ROW_CHANGE: “When you specify this hint, the operation is retried when the ORA_ROWSCN for one or more rows in the set has changed from the time the set of rows to be modified is determined to the time the block is actually modified.”

The use of those hints, however, is only recommended for pretty specific ends and should be avoided if possible. Not only for having some related bugs, but to add some complexity to known operations like bulk inserts and similar.

Other important hint is the Result Cache Hint, mentioned some months ago, under Result Cache Post.

Cheers!