Dynamic database dumping

Several methods are studied for dynamically creating a dump copy of a database while the database is on-line and being updated by user transactions. The methods can be characterized by whether the dump represents the database that existed at the beginning of the dump creation, at the end, or sometime in the middle. The methods are analyzed to understand the performance tradeoffs between alternate methods. The methods vary in the time required to create the dump and the amount of extra storage needed. A key parameter of a given system is shown to be the ratio of the rate at which database entities are copied into the dump to the rate at which database entities are updated. For certain methods to work, the ratio must exceed one. However, by combining two methods into a hybrid scheme, the ratio need only exceed one half.