Work item data volume can grow to a size where hundreds of megabytes of database storage is required. The Purge/Archive wizards enable you to use an agent to automatically delete old work item data from the respective tables or store them in archive files. Purging and archiving old work items and their related history and attachment records helps maintain system performance by reducing database processing demands.
You can refer following link also which will give more information on this.
Thanks for the explanation, but this information i know. I need more detailed informations regarding the internal logic of this function and the responsible rules, so that i can start an investigation by my own.
Background is, that i must know, how the functionality is selecting the attachments from the database. Is it using the OOTB datapages to get the attachments to a case or is it going directly on the database, with another logic? Reason for this questions is, that i have to create an own class Data-WorkAttach-File-XYZ, which is also connected to an own database table. Also the OOTB datapages will not read this attachments and so i need to find out, if this instances of my class are also considered from the purge / archive agent or if the logic must be enhanced to consider it.