Mapping locations of logical volume records on a physical stacked volume

A method for accessing host data records stored in a virtual tape storage (VTS) system, the method comprising:

• building a mapping table that comprises a plurality of entries, wherein each entry includes a physical block ID (PBID) correlated to a starting logical block ID (SLBID) stored to the VTS system, wherein the mapping table is created while a logical volume is being copied to sequential access storage media of the VTS system;
• receiving a mount request to access at least one host data record in the VTS system, the mount request including at least:
• a SLBID that corresponds to the at least one requested host data record;
• a block count field indicating a number of physical blocks to return;
• and
• a block size field indicating a size of each physical block;
• determining a PBID that corresponds to the SLBID using the mapping table, wherein when the mapping table does not have an entry for the SLBID, a highest PBID that corresponds to a SLBID that is lower than the requested SLBID is determined to be the PBID that corresponds to the SLBID to ensure that the at least one requested host data record is retrieved;
• accessing at least one physical block on a sequential access storage medium corresponding to the PBID, wherein the block count field is used to determine a minimum number of physical blocks to retrieve to ensure that the at least one requested host data record is retrieved;
• and
• outputting the at least one physical block corresponding to the PBID without outputting an entire logical volume that the at least one physical block is stored to.