SQL with iseries navigator vs sql greenscreen session

Hi all,

After fixing a program I need to update the client records that have been wrongly modified.

To display the records in a STRSQL session, I did this :

with TEMP_FILE as (
SELECT RCLTNO FROM REF_FIiLE join CLT_FILE on RCLTNO = CCLTNO
WHERE etc GROUP BY etc)

select CCLTNO
from CLT_FILE join TEMP_FILE on
CCLTNO =RCLTNO

No problems up to there. Now, how should I change the final select to update the records in CLT_FILE?

Before typing UPDATE, I did this :

SELECT CCLTNO FROM CLT_FILE
WHERE CCLTNO IN (
SELECT RCLTNO FROM TEMP_FILE )

After 8 minutes and no response I'm going to kill the session with *SYSTEM/ENDRQS.

Now , in iSeries navigator, the same request takes 40 seconds.

Anyone tell me what's happening here ? Thanks