This mode of single instancing is used to store e-mail attachments in the archive only once even if they are attached to multiple different e-mails. An e-mail is divided by an e-mail processing subsystem into a body and attachments that are stored separately. The subsystem stores attachments that contain the same binary data only once (as a single instance).
A checksum is used to identify same binary data of attachments. To compare binary files and to delete identical ones, an asynchronous process is used. A binary attachment is initially always stored in the archive to calculate its checksum. If a duplicate object is found, it will be used instead, and the duplicate binary file will be deleted asynchronously at a later point in time. A reference counting mechanism is used to ensure that only those binary objects are deleted that are no longer in use by any document.
To enable this mode of single instancing, set this up in the AdminClient [UM AdminClient]:
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In the Archives configuration room, select Single Instance for a realm.
See AdminClient user manual chapter Realms configuration for details.
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In the E-Mail configuration room, select Attachment Single Instancing.
See AdminClient user manual chapter ImageMaster settings for details.