I don't know of any documents which discuss this, but the VMPS configuration file is just a text file that lists MAC addresses and VLAN names in addition to some other settings. It's hard to imagine the database that this text file is converted to being too much larger than the text file itself.
I don't know exactly what conclusions can be drawn from this, but here are two lines from "show proc mem" (the only 2 that seem relevant to VMPS) on a 6509 using VMPS with about 300 MAC addresses:
PID.....TTY....Allocated....Freed....Holding....Process
--------------------------------------------------
9..........-2............16..............0............16......VMPS_Task
68........-2......5192160..5169088...23072...DVLAN_Rx
These numbers are in bytes. The VMPS config file is around 16K in size, so the apparent usage of 23K by the DVLAN_Rx process could be the VMPS DB.