I allocated storage pool volumes big enough to fill an empty 3390 disk device
on  MVS.  I was able to allocate 2 storage volumes: one 1150 and the other 1190
MB.  A map of the volume looks like this:

#of tracks dataset name
     1       *** VOLUME LABEL ***
    29       SYS1.VTOCIX.VSYS026
    45       ****** VTOC ******
    30    V  SYS1.VVDS.VSYS026
 24540   V  ADSM1.STORAGE.POOL006.DATA
 25395   V  ADSM1.STORAGE.POOL007.DATA
    45       --- FREE SPACE ---
    15    A  *FREE ALTERNATE TRACK(S)*
 50100      *TOTAL TRACKS

The device capacity is about 2800 MB.  With all but 10 cyl. allocated to ADSM
databases, I expected  2800 MB of disk storage, instead I got only 2340 MB.
What happened to the other 500MB?  Anyone have any ideas?