Pega 7 platform relational database holds the rules, data instances, work items, history and other concrete objects from the internal classes of your Pega 7 Platform system. External classes, by definition correspond to tables in other databases are not part of the Pega 7 database. For example, if your data is available in the external database and you want to use it in the Pega application then you have the option to connect to the external database, for more information here.
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Rollback :- Use this method to cancel or withdraw any previous uncommitted changes to the PegaRULES database (and to external databases accessed from an external class) from the current Thread. All pending Obj-Save and Obj-Delete methods are canceled.