Increasing VM size on a VAX under 4.2

[George White]

We have some applications that really want more than the 6 Mbytes
that the 4.2 distribution sets as the maximum data size.  I more or
less know how to change it (based on what measly documentation I
have) but am not sure of the ramifications.  What effects does it
have on kernel memory requirements, performance etc?  Are there
any gotchas to worry about?  What are preferable alternatives to 
6 Mbytes (why isn't a power of 2)?  Any helpful info and insight 
would be greatly appreaciated.  

				Thanks in advance 

				George White

			{cae780,turtlevax}!weitek!george