Strange locks in ONLINE

Hi all, I've a little problem that i cannot understand. I'm a newbie on ONLINE but what happening seems to me a really strange thing. I've a customer that has an application running with RDS 4.12.??? on a db ONLINE 5.03.??? (running on DPX 490 with AIX version 3.2.5). Some terminal are connected via modem and dedicated link from other town (not using C/S application but as remote terminal). From one of this remote site they received a LOCK message (252 error with 113 ISAM error) on a table call "tabmag" (apparently) running a select count (*) from tabmag. From the central site , the customer has logged in with the same username of the remote site and runned the application without receiving error (obviously when the remote site was receiving error ). Hunging a running ( only READING ) process that was reading other tables, the error stopped. What can i check ? Did ONLINE create some locks on system tables ?? Thanks in advance and sorry form my not good english Pierluigi "PIGI" Frullani Frumar srl pigi@frumar.it