METHOD AND APPARATUS FOR CONCURRENT MODIFICATION OF AN INDEX TREE IN A TRANSACTION PROCESSING SYSTEM

• Main Authors: FRANK ELIOT LEVINE, CHANDRASEKARAN MOHAN
• Format: Patent
• Language: English
• Published: 30.11.1995
• Subjects: CALCULATING; COMPUTING; COUNTING; ELECTRIC DIGITAL DATA PROCESSING; PHYSICS

A METHOD AND APPARATUS FOR CONCURRENT MODIFICATIONS OF AN INDEX TREE IN A TRANSACTION PROCESSING SYSTEM.THE INDEX TREE INCLUDES AT LEAST ONE ROOT NODE HAVING A KEY RECORD REFERENCE TO ONE OR MORE NODES IN A NEXT LOWER ORDERED LEVEL AND AT LEAST ONE BOTTOM NODE PROVIDING ACCESS TO KEY RECORDS. TRANSACTIONS INCLUDING A STRUCTURE MODIFICATION OPERATION ARE PERFORMED BY TRAVERSING THE INDEX TREE TO THE SELECTED NODE AND THEN SETTING AN INDICATION OF THE PENDENCY OF A STRUCTURE MODIFICATION OPERATION. CONCURRENT KEY RECORD INSERTS OR DELETES ARE PREMITTED THROUGHTOUT THE INDEX TREE WHERE NO INDICATION OF A PENDING STRUCTURE MODIFICATION OPERATION IS PRESENT AND ARE DELAYED WHERE A PENDING STRUCTURE MODIFICATION OPERATION IS INDICATED. SIMILARLY, TRANSACTIONS WHICH INCLUDE A KEY RECORD DELETE MAY REQUIRE A STRUCTURE MODIFICATION OPERATION IN THE EVENT THE TRANSACTION DOES NOT REACH NEW POINT OF CONSISTENCY AND MUST BE UNDONE.THEREFORE, AN INDICATION OF EACH KEY RECORD DELETE WHICH HAS NOT YET REACHED A NEW POINT OF CONSISTENCY IS SET AND CONCURRENT KEY RECORD INSERTS OR DELETES ARE ALSO DELAYED UNTIL THE POSSIBILITY OF A STRUCTURE MODIFICATION OPERATION IS COMPLETED. (FIG. 3)