LDS is a VSAM dataset in name only. It has unstructured 4k (4096 bytes ) fixed size CT's which do not contain control fields and therefore from VSAM's standpoint they do not contain any logical records. There is no free space, and no access from Cobol. Can be accessed by DB2 and IMS fast path datasets. LDS is essentially a table of data maintained on disk. The 'table entries' must be created via a user program and can only be logically accessed via a user program. When passed, the entire LDS must be mapped into storage, and then data is accessed via base and displacement type processing.