Call Prepare to have the BDE and a remote database server allocate resources for the query and to perform additional optimizations. Preparing a query consumes some database resources, so it is good practice to call UnPrepare once the query is no longer needed. 

If the query will only be executed once, the application does not need to explicitly call Prepare or UnPrepare. Executing an unprepared query generates these calls automatically. However, if the same query is to be executed repeatedly, it is more efficient to prevent these automatic calls by calling Prepare and UnPrepare explicitly.

ExecSQL 

Open 

UnPrepare 

Using TQuery