Hi,

The system stores attachments in instances of these concrete classes, subclasses of the Data-Work Attach- class:

Data-WorkAttach-File, Data-WorkAttach-Note, Data-WorkAttach-URL, Data-WorkAttach-ScreenShot, Data-WorkAttach-ScanDocument, Data-WorkAttach-ECM

By default, work item attachments are stored as rows of the pc_data_workattach table.

Link-Attachment class instances store pzInsKey 's of the attachment and the work object in an instance so that we will know that the attachment and work object are linked.

Answer1:

If the attachment is of type File, then it is stored as an instance of Data-WorkAttach-File in pc_data_workattach table.

Answer2:

A file attachment for a work object is an instance of Data-WorkAttach-File. The attachment is connected to its work object through a link object, an instance of Link-Attachment.

Answer3:

Using Link-Objects method you can add attachment to a work object.

You can refer to below articles for more details.

https://community.pega.com/knowledgebase/articles/process/how-create-activities-attach-files-work-objects

https://community.pega.com/sites/default/files/help_v63sp1/Content/methods/link-objects/link-objects.htm

https://community.pega.com/sites/default/files/help_v718/concepts/casemanagement/con_conceptsattachments.htm