As an optimisation of memory space it could be interesting to use the ordered index as primary key. This requires the following adaptions. 1) TUX must handle ACCKEYREQ and ACC_COMMITREQ and ACC_ABORTREQ. TUX will still use ACC for lock handling but will ensure uniqueness constraint on primary key. 2) Build index during system restart must be performed after executing the UNDO log but before executing the REDO log. 3) Create table must create an ordered index and ensure that the table is not used before the index have been created.