LOB changes not wirtten in redo logs?

Question

Hi there,
im just evaluating a one replikation software for syncronizing Oracle Databases. We use a 9.2 Database Standard Edition one.
I was told by a consultant, that LOB tables cannot be syncronized, because the changes are not written into the redologs. Is this true?
Thanks, Sven

Answer 1

Sven,
I belive there is no such restriction in Oracle.
consider the test case (Oracle 9.2.0.6 Ent.Edition, Windows 2003):
SQL> ALTER DATABASE ADD SUPPLEMENTAL LOG DATA;
Database altered.
SQL> create table test_lob(lob clob) ;
Table created.
SQL> alter system switch logfile;
System altered.
SQL> declare
2 l_lob CLOB ;
3 begin
4 insert into test_lob values (empty_clob()) returning lob into l_lob ;
5 dbms_lob.writeappend(l_lob, 4, 'test') ;
6 end ;
7 /
PL/SQL procedure successfully completed.
SQL> alter system switch logfile;
System altered.
SQL> EXECUTE DBMS_LOGMNR.ADD_LOGFILE( LOGFILENAME =>'j:\orant\archive_logs\Arc1_731.arc', OPTIONS => DBMS_LOGMNR.NEW);
PL/SQL procedure successfully completed.
SQL>
SQL> EXECUTE DBMS_LOGMNR.START_LOGMNR(OPTIONS => DBMS_LOGMNR.DICT_FROM_ONLINE_CATALOG);
PL/SQL procedure successfully completed.
SQL> select scn, sql_redo from V$LOGMNR_CONTENTS;
returns
1101810606178,set transaction read write;
1101810606178,insert into "OBIDEM00"."TEST_LOB"("LOB") values (EMPTY_CLOB());
1101810606178,update "OBIDEM00"."TEST_LOB" set "LOB" = 'test' where "LOB" = EMPTY_CLOB() and ROWID = 'AAAV7JAABAAAacJAAA';
as you can see the LOB related statements are in the archived log, means they were written in redo log.
The question is how the LOB gets created in your case? If it is loaded through the direct-path load or you are using NOLOGGING option then it is possible that the LOB data would not appear in the redo log. In this case it is not the Oracle restriction, but the peculiarity of your application
Mike