Control-M: 22_NAQ_NONSAP - Event: JOB NOT OK App: LYNX-IS-BI-QA-G2J Job: RMAN-INCREMENTAL-BACKUP Folder: 9N2QA22_LYN-DATABASE-BW1_PRI
incident came after Q4 OS patching activity  
observer node was not started. after starting observer node backup completed successfully 
hence resolving this incident