You can use the lssvcevents command on the HMC to display a history of DLPAR operations.
For example, to display the history for DLPAR memory operations for the last 300 days:
hscroot@hmc61:~> lssvcevents -t console -d 300 | grep -i mem | grep DLPAR
time=04/22/2013 13:48:52,text=HSCE2203 User name hscroot: DLPAR Add memory resources to partition aixlpar2 succeeded on managed system 795-2
time=04/22/2013 13:47:11,text=HSCE2203 User name hscroot: DLPAR Add memory resources to partition aixlpar20 succeeded on managed system 795-1
time=04/20/2013 23:10:16,text=HSCE2203 User name hscroot: DLPAR Add memory resources to partition aixlpar27 succeeded on managed system 795-1
time=04/17/2013 14:16:57,text=HSCE2203 User name hscroot: DLPAR Add memory resources to partition aixlpar21 succeeded on managed system 795-2
time=04/17/2013 14:14:22,text=HSCE2203 User name hscroot: DLPAR Add memory resources to partition aixlpar10 succeeded on managed system 795-1
time=04/16/2013 13:48:46,text=HSCE2203 User name hscroot: DLPAR Add memory resources to partition aixlpar28 succeeded on managed system 795-2
time=04/16/2013 13:47:25,text=HSCE2203 User name hscroot: DLPAR Add memory resources to partition aixlpar11 succeeded on managed system 795-1
time=04/15/2013 13:11:02,text=HSCE2203 User name hscroot: DLPAR Add memory resources to partition aixlpar89 succeeded on managed system 795-2
time=04/12/2013 10:31:31,text=HSCE2203 User name hscroot: DLPAR Add memory resources to partition aixlpar76 succeeded on managed system 795-2
time=04/12/2013 10:29:06,text=HSCE2203 User name hscroot: DLPAR Add memory resources to partition aixlpar3 succeeded on managed system 795-1
To display the history for DLPAR processor operations for the last 300 days:
hscroot@hmc61:~> lssvcevents -t console -d 300 | grep -i processor | grep DLPAR
time=04/23/2013 12:46:10,text=HSCE2209 User name hscroot: DLPAR Add processor resources to partition aixlpar20 succeeded on managed system 795-1
time=04/23/2013 12:44:49,text=HSCE2210 User name hscroot: DLPAR Add processor resources to partition aixlpar20 failed on managed system 795-1
time=04/22/2013 14:33:54,text=HSCE2211 User name hscroot: DLPAR Remove processor resources from partition aixlpar31 succeeded on managed system 795-2
time=04/22/2013 14:31:41,text=HSCE2209 User name hscroot: DLPAR Add processor resources to partition aixlpar31 succeeded on managed system 795-2
time=04/22/2013 13:45:48,text=HSCE2209 User name hscroot: DLPAR Add processor resources to partition aixlpar34 succeeded on managed system 795-1
time=04/21/2013 01:21:33,text=HSCE2209 User name hscroot: DLPAR Add processor resources to partition aixnim1 succeeded on managed system 795-1
time=04/19/2013 14:33:20,text=HSCE2211 User name hscroot: DLPAR Remove processor resources from partition aixlpar34 succeeded on managed system 795-1
time=04/19/2013 11:51:22,text=HSCE2211 User name hscroot: DLPAR Remove processor resources from partition aixlpar32 succeeded on managed system 795-2
time=04/19/2013 11:49:09,text=HSCE2209 User name hscroot: DLPAR Add processor resources to partition aixlpar32 succeeded on managed system 795-2
time=04/16/2013 14:49:05,text=HSCE2211 User name hscroot: DLPAR Remove processor resources from partition aixlpar6 succeeded on managed system 795-2
time=04/15/2013 16:26:48,text=HSCE2211 User name hscroot: DLPAR Remove processor resources from partition aixlpar2 succeeded on managed system 795-1
time=04/15/2013 16:25:03,text=HSCE2211 User name hscroot: DLPAR Remove processor resources from partition aixlpar2 succeeded on managed system 795-1
time=04/15/2013 16:19:52,text=HSCE2211 User name hscroot: DLPAR Remove processor resources from partition aixlpar10 succeeded on managed system 795-1
time=04/15/2013 16:17:42,text=HSCE2211 User name hscroot: DLPAR Remove processor resources from partition aixlpar50 succeeded on managed system 795-1
time=04/15/2013 16:17:00,text=HSCE2211 User name hscroot: DLPAR Remove processor resources from partition aixlpar60 succeeded on managed system 795-1
time=04/15/2013 16:15:36,text=HSCE2211 User name hscroot: DLPAR Remove processor resources from partition aixlpar22 succeeded on managed system 795-1
time=04/15/2013 16:14:17,text=HSCE2211 User name hscroot: DLPAR Remove processor resources from partition aixlpar31 succeeded on managed system 795-1
time=04/15/2013 16:12:19,text=HSCE2209 User name hscroot: DLPAR Add processor resources to partition aixlpar45 succeeded on managed system 795-1
time=04/15/2013 16:11:19,text=HSCE2211 User name hscroot: DLPAR Remove processor resources from partition aixlpar11 succeeded on managed system 795-1
time=04/15/2013 16:02:47,text=HSCE2209 User name hscroot: DLPAR Add processor resources to partition aixlpar12 succeeded on managed system 795-1
time=04/15/2013 16:01:44,text=HSCE2211 User name hscroot: DLPAR Remove processor resources from partition aixlpar56 succeeded on managed system 795-1
time=04/15/2013 15:45:25,text=HSCE2210 User name hscroot: DLPAR Add processor resources to partition aixlpar55 failed on managed system 795-1
time=04/15/2013 15:20:07,text=HSCE2210 User name hscroot: DLPAR Add processor resources to partition aixlpar45 failed on managed system 795-1
time=04/15/2013 14:45:15,text=HSCE2209 User name hscroot: DLPAR Add processor resources to partition aixlpar51 succeeded on managed system 795-1