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clock March 11, 2016 21:19 by author Administrator



Hibernate 5 : generator class=“sequence” not working

clock March 3, 2016 18:54 by author Administrator

after upgrade hibernate 4 to 5 sequence not working and hibernate get next val from hibernate_sequence  but 

I solved it by re-configuring mapping in the HBM file from:

<generator class="sequence">

           <param name="sequence">PRODUCT_ID_SEQ</param>

</generator>

to:

<generator class="org.hibernate.id.enhanced.SequenceStyleGenerator">

          <param name="prefer_sequence_per_entity">true</param>

          <param name="optimizer">none</param>

          <param name="increment_size">1</param>

          <param name="sequence_name">PRODUCT_ID_SEQ</param>

</generator> 

ref:http://stackoverflow.com/questions/2155376/how-to-use-existing-oracle-sequence-to-generate-id-in-hibernate


Oracle Table Flash Back Query

clock March 2, 2016 21:31 by author Administrator

From Oracle Ver. 9i Oracle has introduced Flashback Query feature.  It is useful to recover from accidental statement failures. For example, suppose a user accidently deletes rows from a table and commits it also then, using flash back query he can get back the rows.

Flashback feature depends upon on how much undo retention time you have specified. If you have set the UNDO_RETENTION parameter to 2 hours then, Oracle will not overwrite the data in undo tablespace even after committing until 2 Hours have passed. Users can recover from their mistakes made since last 2 hours only.

For example, suppose John gives a delete statement at 10 AM and commits it. After 1 hour he realizes that delete statement is mistakenly performed. Now he can give a flashback  AS.. OF query to get back the deleted rows like this.

Flashback Query

SQL>select * from emp as of timestamp sysdate-1/24;

Or

SQL> SELECT * FROM emp AS OF TIMESTAMP 
      TO_TIMESTAMP('2007-06-07 10:00:00', 'YYYY-MM-DD HH:MI:SS')

 

CoolCool

Cool

Cool

Cool

Cool

 ref http://www.oracle-dba-online.com/flash_back_features.htm


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