Conference ulysse::rdb_vms_competition

1178.0. "DB2/Rdb similarities..." by NEWOA::JONES_S (Declining fdl - ifdl,ufdl...) Sat Aug 08 1992 11:45

    Hi All,
    
    I'm looking at a DB2 to Rdb conversion, and have a few questions:
    
    1) TIME STAMP in DB2... is it updated at verb time, or at transaction 
       time ?
    
       e.g. START TXN
    		UPDATE T1 time_now VALUE TIME STAMP;
    		UPDATE T1 time_now VALUE TIME STAMP;
    		UPDATE T1 time_now VALUE TIME STAMP;
    	    COMMIT;
       On Rdb I believe the time_now will have the same value three times,
       what is the result on DB2 ?
    
    
    2) Reading a report on DB2 it seems to have a "SEQUENTIAL PRE-FETCH"
       option which will read data into buffers before the program requires
       the data -  a little like read-ahead in RMS. Is this true or is it
       just FUD spread by someone with little understanding ?
    
       The description says DB2 will default to reading in 256K buffers of
       data ahead of the processing.
    
    The application itself contains some heavy batch work, with lots of
    reports, and produces 2 million lines of printout every night !
    
    Database size is about 7 Gigabytes on DB2.
    
    TP monitor or online is IMS/DC, so this will involve lots of work !
    
    Thanks All
    
    Steve J (who will be back on 18-Aug-1992)...

CURENT_TIMESTAMP is what you should use:

!
update SALARY_HISTORY
 set salary_end=current_timestamp
where employee_id='00169';
1 row updated
select salary_end from SALARY_HISTORY where employee_id='00169';
 SALARY_END
 10-AUG-1992 11:11:36.12
1 row selected
!
update SALARY_HISTORY
 set salary_end=current_timestamp
where employee_id='00164';
1 row updated
select salary_end from SALARY_HISTORY where employee_id='00164';
 SALARY_END
 10-AUG-1992 11:11:35.56
1 row selected
!
update SALARY_HISTORY
 set salary_end=current_timestamp
where employee_id='00166';
1 rows updated
select salary_end from SALARY_HISTORY where employee_id='00166';
 SALARY_END
 10-AUG-1992 11:11:35.80
1 row selected

    re: .1
    
    Yes, but does it have the same granularity under DB2 as Rdb !