This variable is new in 5.0.13, 6.0.4 and 6.5.4
SPR# RGET5K627Q - This fix reduces the likelihood of duplicate partition
numbers used in IPC keys on Unix, and provides a Notes.ini parameter,
"PARTITION_KEYNUMBER", to handle any remnant collisions. This regression was
introduced in 5.0.7 and has been fixed in 5.0.13, 6.0.5, and 6.5.4.
Note: You must shut down the server before enabling this
Lotus Notes/Domino 5.0.13
Lotus Notes/Domino x.x.x