[Question]OnBar performance problem

I have question about OnBar performance. One of my site uses OnBar with Informix Product : Informix 7.23UC1 System : IBM SPNODE OS : AIX 4.1.3 Backup Device : StorageTek TAPE Array Storage Manager : SCH Storage Manager The StorageTek TAPE Array can backup multiple host via network. And SCH Storage Manager softwares are both installed on BACKUP SERVER and BACKUP CLIENT machine. IDS 7.23UC1 is on BACKUP CLIENT machine. The performance used to be 17 minutes for rootdbs. But now it takes several hours to complete rootdbs backup without any change in data/system!! Any other BACKUP CLIENT(including Informix on other CLIENT)'s performance is not changing. Only this IDS on this IBM SPNODE is problem. And while onbar doing his job, I checked 'onstat -u'. The onbar session's nread increases 16 per minutes.... On the other machine in increases much faster. So, we asked SCH Storage Manager engineer. He told us pump up the Read Ahead parameters.(They are 50/30 now.) This would help ? Is there anybody who has other ideas? I attach onconfig/bar_action.log Thanks in advance. PS : Any other OLTP/DSS queries' performances are good just like before