v  The  server  supports  online-spare  memory.  This  feature  disables  the  failed 
memory  from  the  system  configuration  and  activates  an  online-spare  pair  of 
DIMMs  to  replace  the  failed  active  DIMM  pair.  See  “Online-spare  memory”  on 
page  16  for  more  information  about  online-spare  memory  and  the  DIMM 
configuration  that  is  required. 
v  You  can  enable  either  online-spare  memory  or  memory  mirroring,  but  not  both  at 
the  same  time.  Online-spare  memory  provides  more  memory  capacity  than 
mirroring;  mirroring  provides  better  memory  protection  but  less  memory  capacity 
than  online-spare  memory. 
v  When  you  install  or  remove  DIMMs,  the  server  configuration  information 
changes.  When  you  restart  the  server,  the  system  displays  a  message  that 
indicates  that  the  memory  configuration  has  changed.
 
 
To  install  a  DIMM,  complete  the  following  steps: 
 
1.  Read  the  safety  information  that  begins  on  page  v  and  “Installation  guidelines” 
on  page  9. 
 
2.  Turn  off  the  server  and  peripheral  devices,  and  disconnect  the  power  cord  and 
all  external  cables. 
 
Attention:  In  a  dc  power  environment,  only  trained  service  personnel  other 
than  IBM  service  technicians  are  authorized  to  connect  or  disconnect  power  to 
the  dc  power  supply.  See  the  documentation  that  comes  with  each  dc  power 
supply. 
 
3.  Remove  the  server  cover. 
 
Attention:  To  avoid  breaking  the  retaining  clips  or  damaging  the  DIMM 
connectors,  open,  and  close  the  clips  gently.
 
14  IBM  System  x3650  Type  7979:  Installation  Guide