By default, the Database Connectors for MSSQL run time applies the same READ logic on a previously-read record as is used for the Vision indexed file system. Instead of sending another request to MSSQL to read the same record, the run time gets the record from cache. This behavior is referred to as Cached Read and can improve performance.
A_MSSQL_NO_CACHED_READ controls this behavior. By default cached read is enabled. It can be disabled by setting A_MSSQL_NO_CACHED_READ to true or 1.
If the last operation was a successful READ with LOCK and the next operation is a READ with LOCK on the same key with the same key value then the cached record returneds without accessing the database. A trace file entry is made that says cached read.