Extending Flashback Data Archive in 12c

Flashback Data Archive (previously called Total Recall) has been around for a long time now. For those unfamiliar with it, (and by the way, if you are on Enterprise Edition, you should be familiar with it, because its a free feature), here is a very quick primer.

Create a tablespace to hold your history, and create a flashback archive using that space allocation.

SQL> create tablespace SPACE_FOR_ARCHIVE
  2  datafile 'C:\ORACLE\DB11\ARCH_SPACE.DBF' 
  3  size 100M;

Tablespace created.

  2  TABLESPACE space_for_archive

Flashback archive created.

Then add your tables to the archive. Some tables will be created automatically to support being able to record all of the changes to that table for as long as the archive duration specifies


Table altered.

SQL> select table_name
  2  from   user_tables
  3  /


And then voila! We can track changes to our table over time, well beyond the typical undo_retention setting for the database.

SQL> select empno, ename, job, sal, comm,
  3     ,nvl(VERSIONS_OPERATION,'I') op
  4  from EMP
  5  versions between timestamp
  6    timestamp '2014-02-11 20:12:00' and
  7    systimestamp
  8  order by empno;

     EMPNO ENAME      JOB              SAL       COMM TS           O
---------- ---------- --------- ---------- ---------- ------------ -
      7369 SMITH      CLERK            806            08.10.51 PM  I
      7369 SMITH      SALES           8060       1000 08.12.10 PM  U
      7499 ALLEN      SALESMAN        1606  300000000 08.10.51 PM  I
      7521 WARD       SALESMAN        1256  500000000 08.10.51 PM  I
      7566 JONES      MANAGER         2981            08.10.51 PM  I
      7900 JAMES      CLERK            956            08.10.51 PM  I
      7902 FORD       ANALYST         3006            08.10.51 PM  I
      7934 MILLER     CLERK           1306            08.10.51 PM  I
      7934 MILLER     CLERK           1306            08.12.10 PM  D

But sometimes we want to know more about the history. We want to know who did the change, what machine were they on, etc etc. Auditors tend to be a little snippy about those kind of things Smile

  • You: “I can confirm that the SALARY field was updated at 9:01am on January 25th”
  • Auditor: “And who did that change?”
  • You: “Er….um…..someone”

But it might not be practical to augment all of your tables with WHO, WHEN, WHERE etc columns to capture that information. That might involve a lot of application changes and testing.

If you’re on 12c, you might be in luck. Flashback Data Archive can capture additional information, assuming your application is taking advantage of the myriad of instrumentation facilities offered by the database.

We simply turn on context tracking, which can capture information on a per transaction basis

SQL> begin
  2    dbms_flashback_archive.set_context_level(
  3        level=> 'ALL');
  4  end;

PL/SQL procedure successfully completed.

Now when we perform changes to the table, we can look at the transaction ID (XID) for that change.

SQL> update EMP
  2  set    sal = sal*10
  3  where  empno = 7499;

1 row updated.

SQL> commit;

SQL> select XID from SYS_FBA_HIST_510592;


And using that XID, we can pick up the context information about that transaction

SQL> set serverout on
SQL> begin
  2    dbms_output.put_line(
  3      dbms_flashback_archive.get_sys_context (
  4         '09000B00C7080000', 'USERENV', 'SESSION_USER'));
  6    dbms_output.put_line(
  7      dbms_flashback_archive.get_sys_context (
  8         '09000B00C7080000', 'USERENV', 'HOST'));
 10    dbms_output.put_line(
 11      dbms_flashback_archive.get_sys_context (
 12         '09000B00C7080000', 'USERENV', 'MODULE'));
 13  end;
 14  /

How much more ? Well, quite a lot actually !


 Name                      Null?    Type
 ------------------------- -------- ------------------
 XID                                RAW(8)
 ACTION                             VARCHAR2(256)
 CLIENT_IDENTIFIER                  VARCHAR2(256)
 CLIENT_INFO                        VARCHAR2(256)
 CURRENT_SCHEMA                     VARCHAR2(256)
 CURRENT_USER                       VARCHAR2(256)
 DATABASE_ROLE                      VARCHAR2(256)
 DB_NAME                            VARCHAR2(256)
 GLOBAL_UID                         VARCHAR2(256)
 HOST                               VARCHAR2(256)
 INSTANCE_NAME                      VARCHAR2(256)
 IP_ADDRESS                         VARCHAR2(256)
 MODULE                             VARCHAR2(256)
 OS_USER                            VARCHAR2(256)
 SERVER_HOST                        VARCHAR2(256)
 SERVICE_NAME                       VARCHAR2(256)
 SESSION_USER                       VARCHAR2(256)
 SESSION_USERID                     VARCHAR2(256)
 SESSIONID                          VARCHAR2(256)
 TERMINAL                           VARCHAR2(256)
 SPARE                              VARCHAR2(256)

And since we can use our flashback query syntax to pick up all of the transaction ID’s

SQL> select empno, ename, job, sal, comm,
  3  from EMP
  4  versions between timestamp
  5    timestamp '2014-02-11 20:12:00' and
  6    systimestamp
  7  order by empno;

     EMPNO ENAME      JOB              SAL       COMM VERSIONS_XID
---------- ---------- --------- ---------- ---------- ----------------
      7369 SMITH      CLERK            806
      7369 SMITH      SALES           8060       1000 09001C00E04A0000
      7499 ALLEN      CLERK          16060  300000000 0A000A0024080000
      7499 ALLEN      SALESMAN       16060  300000000 09000B00C7080000
      7499 ALLEN      SALESMAN        1606  300000000
      7521 WARD       SALESMAN        1256  500000000

we can also take advantage of that new dictionary view SYS.SYS_FBA_CONTEXT_AUD to get all the context information for each transaction.

SQL> select ...
  2  from
  3  (  select
  4         empno, ename, job,
  5         sal, comm, VERSIONS_XID
  6     from EMP
  7     versions between timestamp
  8        timestamp '2014-02-11 20:12:00' and
  9        systimestamp
 11  where e.VERSIONS_XID = a.XID;

Flashback Data Archive is pretty nifty in 12c.


2 thoughts on “Extending Flashback Data Archive in 12c

  1. The strange things about SYS.SYS_FBA_CONTEXT_AUD are follows:
    1. it does not contain any indexes
    2. it resides in SYSTEM tablespace
    3. MOS does not show any hits for it

    It means that if either your transaction volume or the Flashback Archive retention is big enough you will end up with a huge table in your SYSTEM tablespace.
    There are several obvious reasons why it is bad (including not so obvious ones like: http://blog.tanelpoder.com/2008/09/02/oracle-hidden-costs-revealed-part2-using-dtrace-to-find-why-writes-in-system-tablespace-are-slower-than-in-others/ ).

    So, currently, out of the box I do not see that the functionality in question has been designed for high volumes.

    I have been waiting for a while till Oracle provides fine-grained Flashback Archive functionality with more control about what should be archived like:
    1. I do not want to my application be logged. It generates a huge amount of changes
    2. I do want to store in a Flashback Archive any changes generated by non-application users (like the application administrators and support staff). These are small part of changes generated by my application.

    We can accomplish fine-grained auditing using, obviously, FGA, Unified Database Auditing (really neat features), triggers. But we do not have such level of data logging as if we use Flashback Data Archive (particularly, we do not have the image of data before DML) and we do not have a way to easily select our data as we do with Flashback Archive.
    And, of course, we can process all of the redo generated by the production database using GoldenGate/Streams and do whatever we want with it (that’s what I do now to satisfy the complex security requirements of my organization).

  2. Thanks for your comment. MOS note 1073588.1 talks about moving objects out of SYSTEM, and whilst SYS_FBA_CONTEXT_AUD is not specifically mentioned, I would *hypothesize* that this is an oversight and will be picked up in due course.

    Whilst I can’t speak for Support, I imagine you could make a pretty good case for it move to (say) SYSAUX without it being an impact on a running system.

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