Patent ID: 8935294
Filing Date: 2015-01-13
Classification: G06F

Abstract:
1. A method for a database management system (DBMS) to allow accessing and changing column values in a table column while a data type of the table column is being converted from a first data type to a second data type, comprising steps of: creating a replacement column of the second data type to replace a first column having a particular name, wherein said replacement column is a hidden column hidden from users of said DBMS; one or more conversion processes executing to perform migration of said column values from said first column to said replacement column, wherein the migration includes: while at least one value of the first column has not been migrated to the replacement column by the one or more conversion processes, allowing one or more non-conversion processes to execute concurrently with the one or more conversion processes, the one or more non-conversion processes performing transactions to change a certain value in the first column of the table for a set of rows having column values that have already been migrated to the replacement column during said migration, wherein to change a certain value causes automatically converting the certain value to the second data type and inserting the certain value into the replacement column; and during a first downtime period after said one or more conversion processes complete said migration and said transactions complete,