Session Temporal Qualifiers
The SET SESSION statement lets you set session temporal qualifiers in the valid-time dimension, transaction-time dimension, or both dimensions. When a DML or SELECT statement refers to a temporal table but omits a temporal qualifier, the system uses the value of the session temporal qualifier.
A session temporal qualifier of CURRENT VAILDTIME AND CURRENT TRANSACTIONTIME allows applications written prior to the temporal capability to continue functioning without modifications in a non-temporal way on tables that may have been converted to temporal tables.
You can check the session temporal qualifier setting by looking at the Temporal Qualifier field of the output of the HELP SESSION statement. For more information on session temporal qualifiers, see “SET SESSION (Session Temporal Qualifiers)” on page 103. For more information on HELP SESSION, see SQL Data Definition Language.
Note: Best practice is to always use explicit temporal qualifiers on SELECT and DML statements that operate on temporal tables, rather than relying on the default temporal session qua lifers.