IBM 3745 Series Service Functions page 223

CCU Operating Mode
Current Operating
Selected Operating Mode
Mode
SINGLE
TWIN TWIN TWIN TWIN
SBY A SBY B DUAL BACKUP
SINGLE
1 4 4 4 4
TWIN STANDBY A
4 1 3 3 3
TWIN STANDBY B
4
3
1
3
3
TWIN DUAL
4 3 3 1
2
TWIN BACKUP
4
3 3
2 1
Note: Possible results can be:
1. Change Ignored
2. If fallback IS:
active
change IS refused
not active change IS accepted (no IPL needed)
3. If NCP IS:
running change IS refused
not running change IS accepted (IPL needed)
4. Change refused (CDF create or upgrade must be performed before)
A CCU operating mode change can destroy the NCP load modules in the disk
files. The following table shows the effect of an operating mode change:
Current Operating
Selected Operating Mode
Mode
SINGLE TWIN TWIN TWIN TWIN
(NCP A) SBY A SBY B DUAL BACKUP
SINGLE (NCP A) No effect No effect A to B No effect No effect
TWIN STANDBY A No effect
No effect
A to B No effect No effect
TWIN STANDBY B B to A· B to A No effect No effect No effect
TWIN DUAL Destroy Destroy Destroy
No effect No effect
NCP B NCP B NCPA
TWIN BACKUP Destroy Destroy Destroy
No effect No effect
NCP B NCP B NCPA
9-44
3745 Communication Controller