Hi PAVB,

Thanks for your reply but I needed to replace only the appearances in the end of the word.
If the string "_TEST" (by mistake I wrote "_TST") appears in the middle of the word ,then the "replace" command will replace all the appearances.
I've just solved my problem as the following:

Code:
update table
set x=SUBSTR(x,1,length(x)-4)||'TRN1'
where substr(x,instr(x,'_',-1,1)+1,length(x)-instr(x,'_',-1,1))='TEST';
Best regards,
Nir