ORA-01555 Snapshot too old
ORA-01555 is caused by Oracle read consistency mechanism. When you run a select all data refer to the same “Instant”, from the first to the last selected row, for the entire duration of the processing and for how many changes are made on the selected tables from other transaction. When read consistency is not more possibile, the error appear. To solve “ORA-01555” you need to set the parameter of undo_retention and stretch retention. The informations of UNDO is stored in Rollback Segments until the commit or rollback, then these segments are available to be overwritten. The automatic management of UNDO...