Article: Mastering Data History using Oracle's Flashback Data Archive Feature

The Historical data is key for business decisions and having reliable data is very important for organizations. There are frequent implications for both financial and legal data for organizations and having a secure and accurate history of change of data is crucial for business.

Oracle Flashback technology offers significant benefits for database management and recovery. 

Please see the below article how it will help to meet the organizational needs.

Mastering Data History : A Guide using Oracle's Flashback Data Archive Feature
https://www.linkedin.com/pulse/mastering-data-history-guide-using-oracles-flashback-archive?trk=public_profile_article_view

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SELECT without FROM Clause in Oracle 23c

Oracle 23c has many new features and “SELECT without FROM” is one of the features. By using this feature, you can run queries without using FROM clause and specifying table name for testing expressions to get the results which can be easy of use for developers.

You will no longer receive error “ORA-00923: FROM keyword not found where expected” when running expressions to get results in Oracle 23c. 

Here are few examples

Example 1: Run mathematical operations with or without using FROM clause and you will get the result

SQL> select 2+3 from dual;
SQL> select 2+3 ;

Example 2: Select current date with and without using FROM clause and you will get the result.

SQL> Select current_date from dual;
SQL> Select current_date;

Example 3: Select NEXTVAL with and without using FROM clause and you will get the result

SQL> Create sequence empno_seq;

 
SQL> select empno_seq.nextval from dual;
SQL> select empno_seq.nextval ;

Example 4: Pl/SQL block with and without using FROM clause and you will get the result
delcare
v1 number;
begin
select empno_seq.nextval into v1 from dual;
dbms_output.put_line ('v1= '||v1);
end;
/

delcare
v1 number;
begin
select empno_seq.nextval into v1;
dbms_output.put_line ('v1= '||v1);
end;
/

Many other databases such as MS SQL Server, MYSQL support without FROM clause, this will help improve SQL Code portability.

Thanks

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Flashback Data Archive enhancements in Oracle 12c

Flashback feature uses Automatic Undo Management for historical and metadata transactions. Flashback Data archive (FDA) feature introduced in Oracle 11g for undo-based flashback operations, and it is configured using retention time. Flashback data archive supported for multitenant (12.1.0.2 and above versions) as well using local or shared undo configuration.

Oracle 12c (12.1.0.1) has below enhancements in FDA

• Data Hardening
• User context tracking

Data Hardening – This feature helps to associate set of tables for a specific application, so that you can enable Flashback Data archive for all those tables in a single command. Use DMBS_FLASHBACK_ARCHIVE.REGISTER_APPLICATION to register an application

You can create new application using REGISTER_APPLICATION

SQL> Begin
DBMS_FLASHBACK_ARCHIVE.register_application(
application_name => 'ORACLERACEXPERT',
flashback_archive_name => 'FDA1');
end;
/

You can add tables to the application using ADD_TABLE_TO_APPLICATION procedure

SQL> Begin
DBMS_FLASHBACK_ARCHIVE.ADD_TABLE_TO_APPLICATION (

application_name=> 'ORACLERACEXPERT', 

table_name=> 'EMP' , 

schema_name -> 'USER1');
end;
/

SQL> Begin
DBMS_FLASHBACK_ARCHIVE.ADD_TABLE_TO_APPLICATION (

application_name=> 'ORACLERACEXPERT', 

table_name=> 'DEPT' , 

schema_name -> 'USER1');
end;
/

You can remove the tables using REMOVE_TABLE_FROM_APPLICATION procedure from

The application will not enable automatically, use ENABLE_APPLICATION procedure to enable Flashback Data Archive for all tables in the specified application.

SQL> Begin
DBMS_FLASHBACK_ARCHIVE.enable_application(

application_name => 'ORACLERACEXPERT');
end;
/

To disable the application use disable_application procedure

SQL> Begin
DBMS_FLASHBACK_ARCHIVE.disable_application(
application_name => 'ORACLERACEXPERT');
end;
/

User context tracking - By enabling this feature it is easy to track which user made what changes to the table.

Use DMBS_FLASHBACK_ARCHIVE.SET_CONTEXT_LEVEL procedure to Set the user content level and procedure DMBS_FLASHBACK_ARCHIVE.GET_SYS_CONTEXT procedure To Access the context

There are 3 options depending upon how much user context needs to save
ALL – The entire SYS_CONTEXT is stored
TYPICAL – The user context is stored
NONE- Nothing

For ex: - To set context level to ALL
SQL> DBMS_FLASHBACK_ARCHIVE.SET_CONTEXT_LEVEL ( level=>‘ALL’);

You can get the XID from the archive table

SQL> select XID from SYS_FBA_HIST_93222;
XID
----------------
05000A0B7040000

Now with XID you can get the context information using dbms_flashback_archive.get_sys_context procedure


SQL> begin
dbms_output.put_line(dbms_flashback_archive.get_sys_context ('05000A0B7040000', 'USERENV', 'SESSION_USER'));
dbms_output.put_line(dbms_flashback_archive.get_sys_context ('05000A0B7040000', 'USERENV', 'HOST'));
dbms_output.put_line(dbms_flashback_archive.get_sys_context ('05000A0B7040000', 'USERENV', 'MODULE'));
end;
/
USER1
SRVHOST
SQL*Plus

You can get all Transactions ID using below query

SQL> select empno, empname, VERSIONS_XID
from EMP order by empno;

EMPNO EMPNAME VERSIONS_XID
----------- --------------- ---------------------
1              ORARAC    05000A0B7040000

You can use SYS_FBA_CONTEXT_AUD to get context information for each transaction.

There are many Flashback data archive view available and to get the list of all views run below query

SQL> SET PAGESIZE 1000
SQL> SET LINESIZE 600
SQL> COLUMN owner FORMAT A10
SQL> COLUMN table_name FORMAT A25

SQL> SELECT owner, table_name FROM dba_tables WHERE table_name LIKE '%FBA%';

 
OWNER       TABLE_NAME
--------------  -------------------------
SYS              SYS_FBA_FA
SYS              SYS_FBA_TSFA
SYS              SYS_FBA_TRACKEDTABLES
SYS              SYS_FBA_PARTITIONS
SYS              SYS_FBA_USERS
SYS              SYS_FBA_BARRIERSCN
SYS              SYS_FBA_DL
SYS              SYS_FBA_CONTEXT
SYS              SYS_FBA_CONTEXT_AUD
SYS              SYS_FBA_CONTEXT_LIST
SYS              SYS_FBA_APP
SYS              SYS_FBA_APP_TABLES
SYS              SYS_FBA_COLS
SYS              SYS_FBA_PERIOD
SYS              SYS_MFBA_STAGE_RID
SYS              SYS_MFBA_TRACKED_TXN
SYS              SYS_MFBA_NROW
SYS              SYS_MFBA_NCHANGE
SYS              SYS_MFBA_NTCRV

You can refer below Oracle Doc for best practices

FDA - Flashback Data Archive Usage and Best Practices (Doc ID 2370465.1)

Flashback Data Archive provides many benefits for maintaining historic data against tracked tables. The FDA helps to perform undo-based flashback operations for an extended period and take advantage of this feature.

Webinar: Oracle Database 23c Security new features

This Webinar helps you to understand Oracle Database 23c Security new features and head start using these features

Date and time: July 3rd 2023, 8:00am-9:00am
Pacific Daylight Time (San Francisco, GMT-07:00)

This Webinar covers following Topics.

•  SQL Firewall
•  Audit
•  Authentication
•  Authorization
•  Encryption
•  Autonomous Database
•  Other

To register for this Webinar, please send an email to SatishbabuGunukula@gmail.com
You will receive an email confirmation with meeting link or Webinar link will be posted here.

Note that registrations are limited and first come and first serve basis.

For presentation link Click here

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Oracle 19c import issues ORA-31693, ORA-02354, ORA-39002, ORA-39405

When performing import come across the following issue

ORA-31693: Table data object "ORCL"."ITEMCG" failed to load/unload and is being skipped due to error:
ORA-02354: error in exporting/importing data
ORA-39840: A data load operation has detected data stream format error .
ORA-39844: Bad stream format detected: [klaprs_62] [139751105749101] [139751105749012] [4] [2] [2065583] [] []

User may encounter this issue when new column added to a table with cokumn optimization enabled and the same column was modified.

Below are the workarounds

• Use access_method=EXTERNAL_TABLE during export

• Prior export add and drop a dummy column to the problematic table using

SQL> ALTER TABLE <table_name> ADD dummy number;
SQL> ALTER TABLE <table_name> DROP dummy number;

• Take export of failed table and import using CONTENT=DATA_ONLY as tableau structure already imported.

The fix for this bug was initially available on 19.13 and above see if it helps.

Also, I come across below issues when importing data

ORA-39002: invalid operation
ORA-39405: Oracle Data Pump does not support importing from a source database with TSTZ version 33 into a target database with TSTZ version 32.

User may encounter this issue when export from higher time zone version and importing into lower time zone version.

• Patch the target database to higher or equal to source time zone patch or DST TZ version
• Create a database with same time zone and perform export/import

For latest DST patches refer,

• Oracle RDBMS and OJVM DST-related notes
• Updated DST Transitions and New Time Zones in Oracle RDBMS and OJVM Time Zone File Patches (Doc ID 412160.1)

Hope this helps,

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