Method for fault tolerant modification of data representation in a large database

A system for managing a database that includes (i) a plurality of tables, each having a plurality of records, the records of each table being grouped into one or more partitions of each table, (ii) control data describing each of the plurality of tables and the partitions thereof, and (iii) an audit trail describing updates, if any, to the records, the system comprising:

• at least two storage units for storing a plurality of files, each file for holding a partition in a number of fixed-size blocks;
• a processing unit that connects to the storage units and includes:
• a central processor;
• and
• a memory containing a program for managing the database, the program being configured to:
• alter the control information to indicate that each partition of the table has a first format in which each partition is currently stored in the first storage unit;
• update the control information to indicate that each partition of the table is enabled to be stored in a second format;
• select a partition to be restructured;
• copy the blocks of a first file, stored in a first location of the first storage unit and containing the selected partition of the table, from the first storage location to a second file at a second storage location of the second storage unit, while allowing updates to the table, including updates to the selected partition in the first file;
• alter the blocks in the second file to have the second format;
• update any records in the selected partition in the second file based on the audit trail, while allowing updates to the table including updates to the selected partition at the first storage location;
• lock the table to prevent updates to the table, after updating any records in the second file based on the audit trail;
• update any records in the selected partition at the second storage location based on the audit trail, while the table is locked;
• and
• unlock the table to allow updates to the table including the updates to the selected partition at the second storage location.

A computer readable medium having computer-executable instructions for performing a method of restructuring the physical storage of a table in a database, the table having a plurality of records and one or more partitions into which records of the table are grouped, each partition being stored in a file made up of a number of fixed-size blocks, the database further including control information describing the table, associated files and partitions, and including an audit trail describing updates, if any, to the records of the table, the method comprising:

• altering the control information to indicate that each partition of the table has a first format in which each partition is currently stored in a first storage unit;
• updating the control information to indicate that each partition of the table is enabled to be stored in a second format;
• selecting a partition to be restructured;
• copying the blocks of a first file, stored in a first location of the first storage unit and containing the selected partition of the table, from the first storage location to a second file at a second storage location of the second storage unit, while allowing updates to the table, including updates to the selected partition in the first file;
• altering the blocks in the second file to have the second format;
• updating any records in the selected partition in the second file based on the audit trail, while allowing updates to the table including updates to the selected partition at the first storage location;
• locking the table to prevent updates to the table, after updating any records in the second file based on the audit trail;
• updating any records in the selected partition at the second storage location based on the audit trail, while the table is locked;
• and
• unlocking the table to allow updates to the table including updates to the selected partition at the second storage location.

A method of restructuring the physical storage of a table in a database, the table having a plurality of records and one or more partitions into which records of the table are grouped, each partition being stored in a file made up of a number of fixed-size blocks, the database further including control information describing the table, associated files and partitions, and including an audit trail describing updates, if any, to the records of the table, the method comprising:

• selecting a partition to be restructured, the selected partition being stored in a second file with a second format;
• copying the blocks of the second file, stored in a second location of a second storage unit, from the second storage location to a first file at a first storage location of a first storage unit, while allowing updates to the table, including updates to the selected partition in the second file;
• altering the blocks in the first file to have a first format;
• updating any records in the selected partition in the first file based on the audit trail, while allowing updates to the table including updates to the selected partition at the second storage location;
• locking the table to prevent updates to the table, after updating any records in the first file based on the audit trail;
• updating any records in the selected partition at the first storage location based on the audit trail, while the table is locked;
• and
• unlocking the table to allow updates to the table including updates to the selected partition at the first storage location.