bmaxdata=0xN000000

I remember running into this little AIX quirk a while back when I was porting some software to it:

Basically, for some historical reasons AIX OS will allow your application to allocate maximum 256MB of memory per process by default. To use more, you have to use “Large Address Space” memory model so AIX will split memory into 256MB data segments, making possible to reserve more than one segment per single process.