Patent ID: 6216136
Filing Date: 2001-04-10
Classification: G06F,Y10S

Abstract:
A method of performing in a data-base a schema change, such as a complicated soft schema change where a first schema version prior to the schema change is compatible with a second schema version after the schema change, or such as a complicated hard schema change where a first schema version before said schema change is incompatible with a second schema version after said schema change, comprising the steps of:dividing the complicated schema change into three phases, of whicha first phase, a preparatory phase, comprises creating conditions which enable transactions according to said second schema version to be commenced while retaining conditions for enabling transactions according to said first schema version to continue, this first phase being a simple schema change;a second phase, a scan phase, comprises the transmission of data according to said first schema version to data according to said second schema version; and of whicha third phase, a terminating phase, comprises the removal of those units that shall not be present upon completion of a schema change, which is a simple schema change.