CA Vtape VTS supports LBI. As a standard 3480 or 3490 device, Virtual mounts are limited by IBM allocation to a maximum size of 64 KBs (65535 bytes). Any attempt to code a larger block size will result in a 213-68 ABEND.
The Backstore mounts are limited by IBM allocation depending on the type of drive being mounted. The limitations are documented in the IBM DFSMS Using Data Sets manual.
The block size used by Backstore is controlled by the BackstoreBlocksize attribute found in the Group Definitions Sections in the VTGROUP parmlib member. See the CA Vtape VTS Configuration Guide, the Parameter Library (Parmlib) chapter for additional information.