A computer readable storage medium, comprising executable instructions to perform computer-implemented operations, the operations comprising: storing load data in new records of an append only table within a data warehouse, without updating or deleting existing rows in the append only table, wherein the executable instructions to perform storing include executable instructions to allow N different machines to store data to N different regions (200, 202, 204, 206) of memory of the append only table concurrently, wherein storing the load data comprises assigning a first memory region to a first machine, wherein the first memory region is for the first machine to insert records into the append only table, assigning a second memory region to a second machine, wherein the second memory region is for the second machine to insert records into the append only table, and assigning a completion transaction identification number to each write transaction to a memory region of the append only table upon completion of the write transaction; maintaining data change information associated with the load data in a separate update table; and merging data from the append only table with data change information from the update table to supply read data, wherein merging the data comprises reading visible information from the append only table, reading the maintained data change information from the update table, and deleting and updating values from the visible information read from the append only table as specified by the data change information read from the update table to supply the read data, wherein reading the visible information from the append only table comprises computing data visibility by determining an End of File boundary such that data from the start of the memory region to the End of File boundary is visible; wherein visible information is data in the memory region having completion transaction identification numbers that are not greater than a read request transaction identification number of a read request requesting the visible information. storing load data in new records of an append only table within a data warehouse, without updating or deleting existing rows in the append only table, wherein the executable instructions to perform storing include executable instructions to allow N different machines to store data to N different regions (200, 202, 204, 206) of memory of the append only table concurrently, wherein storing the load data comprises assigning a first memory region to a first machine, wherein the first memory region is for the first machine to insert records into the append only table, assigning a second memory region to a second machine, wherein the second memory region is for the second machine to insert records into the append only table, and assigning a completion transaction identification number to each write transaction to a memory region of the append only table upon completion of the write transaction; maintaining data change information associated with the load data in a separate update table; and merging data from the append only table with data change information from the update table to supply read data, wherein merging the data comprises reading visible information from the append only table, reading the maintained data change information from the update table, and deleting and updating values from the visible information read from the append only table as specified by the data change information read from the update table to supply the read data, wherein reading the visible information from the append only table comprises computing data visibility by determining an End of File boundary such that data from the start of the memory region to the End of File boundary is visible; wherein visible information is data in the memory region having completion transaction identification numbers that are not greater than a read request transaction identification number of a read request requesting the visible information.