Abstract: Methods, computer programs, and database systems for protecting one or more database objects are disclosed. The methods include designating one or more database objects for protection and characterizing one or more data storage units by a set of dimensions. The method include, for one or more database objects designated for protection: selecting one or more data storage units to store protection information for the database object based on one or more dimensions, and storing protection information in the one or more selected data storage units.

Abstract: A database system receives a transaction that selects values of a column of a first table based on one or more conditions, the column in the first table being according to a first data type. The database system transforms the first data type to a second, different data type. The selected values of the column according to the second data type are stored in the second table.

Abstract: Methods, computer programs, and database systems for performing a database query to join a column A and a column B on an inequality condition are disclosed. A database includes value-count indexes for columns A and B. Minimum and a maximum values for A and B are determined, using the value-count indexes for A and B, respectively. The method includes defining three or more sets of values in A and B, relative to the minimum and maximum values for B and A, respectively. The method includes generating one or more Cartesian products between values in A and B. The database query is performed on a set of values in A and a set of values in B to generate a partial query result. The method includes merging one or more Cartesian products and the partial query result.

Abstract: Methods, computer programs, and database systems for performing a database query to join two or more tables on a condition are disclosed. Each table includes one or more join columns. Each of the join columns includes zero or more join-column values. The method includes excluding join-column values that do not satisfy the condition, using one or more value-count indexes and performing the database query on non-excluded join-column values.

Abstract: A database system receives a transaction specifying one or more conditions to apply to a first table, and inserts data selected in the transaction into a second. The database system further generates a value list used for compressing a column of the second table, where generating the value list comprises one of inheriting entries of the value list from another value list associated with the first table, and deriving the value list based on the one or more conditions to apply on the first table.

Abstract: Methods, computer programs, and database systems for performing a database query that includes a join on an equality condition are disclosed. The method includes defining two or more first-table partitions and two or more corresponding second-table partitions. The method includes performing the join on the first-table partition and the second-table partition, storing the result, and merging the results.

Abstract: A method, computer program, database system and data structure are disclosed for compressing a decimal type field in a database including one or more tables. Each of the one or more tables includes one or more rows. Each of the one or more rows includes an instance of the decimal type field. Space is allocated in one of P amounts to an instance of the decimal type field in a row, the amount being chosen based on the size of the value being stored in the instance of the decimal type field. One or more presence bits are set in the row to identify the amount of space allocated.

Abstract: A method, computer program, and computer system are disclosed for managing data corruption identified by an application in a storage subsystem. Data requested of the application by a process is copied from a primary storage device in the storage subsystem to a memory. A data integrity check is performed on the data stored in the memory. If the data integrity check succeeds, the data is provided from the application to the process.

Abstract: Detecting data corruption includes receiving one or more blocks of data to be written to a storage device, selecting a portion of the data in the blocks (e.g., one or more bytes or data words), applying a rule to derive information characterizing the selected portion of data (e.g., calculating a checksum for the for the portions of data selected from the block to be written), and storing this information. After the data has been written to the storage device, the store information is used in deciding whether the data has been corrupted.

Abstract: A set of storage disks includes a mirrored pair of disks. Each disk in the pair includes a mirror copy of data stored on the other disk in the pair. For each of the disks in the pair, the data forming the mirror copy is physically located between the center of the disk and the data that is mirrored on the other disk.

Abstract: A set of storage disks includes a mirrored pair of disks. Each disk in the pair includes a mirror copy of data stored on the other disk in the pair. For each of the disks in the pair, the data forming the mirror copy is physically located between the center of the disk and the data that is mirrored on the other disk.