VBIOS.SYS is a fix for these different problems:

APAR PJ03709  Loading into UMB with OEM machines with Extended BIOS data area
APAR PJ03889  Running reboot vector on Model 40 causes hang
APAR PJ03998  Running DOS HIMEM.SYS in VMBOOT on L40 SX and causing hang

The biggest problem is APAR PJ03709.  SYS3176 is common on OEM machines
with Extended BIOS data area while loading into UMBs.  This has been fixed.

To replace, just copy over the file in \OS2\MDOS.  No need to include in
config.sys, since it is loaded automatically.