For LANSA Tables, Yes indicates that the IBM i table was created with SQL the last time it was built (rather than DDS and CRTPF). This value is only set on Checkout from IBM i (or when a LANSA Import is done).
LANSA tables are built with SQL for many reasons, for example, if they include a BLOB or CLOB column. You can force all tables to be built with LANSA SQL. For details, see the option Always Build Using SQL (IBM i) in System Definitions in the Administrators Guide.
For IBM i Tables, Yes indicates that SQL must be used to access the table at execution time. This value is set when loading the Other Table definition. Refer to Load Other Table for further information.
Always build using SQL in Column and Table Defaults in the LANSA for i User Guide.