Overrides the default values for the isolation level and read-only transaction parameters (which are set in the SESAM configuration file), in order to optimize subsequent queries and guarantee database consistency. The overridden values are used for the next transaction only. See the SESAM handbook for detailed explanation of the semantics.
This function can only be called before starting a transaction, not after the transaction has been started already.
The values set by sesam_settransaction() will override the default setting specified in the SESAM configuration file.
Returns TRUE if the values are valid, and the settransaction operation was successful, FALSE otherwise.