The TSO message "LOGON PROCEEDING" actually means that it is NOT proceeding; that message is issued when MVS sees your session has been in a wait state for over 5 minutes, while trying to log on. Most common cause for LOGON PROCEEDING is a delay in allocation (like a RESERVE, or a Lock on Q4, the allocation queue). Back in the SVS operating system, a mount of a disk volume (yes, 2314s and 3330s were mountable) put an Exclusive Lock on Q4 from the time the mount message was issued until the new volume's VTOC had been read ("Vol Verify"), if the DD for the mount had DISP=OLD or NEW. We discovered this delay at State Farm, used SMF to identify which jobs were mounting DISKs (the UCB ADDR were known and in the SMF 4 records), and had the users insert an PGM=IEFBR14 step with DISP=SHR for the mountable volume, and saved over 2000 person-hours of our TSO users.
