Attachment consolidation

The Domino® server employs the Domino® Attachment and Object Service (DAOS) to save significant space at the file level by sharing data identified as identical between databases (applications) on the same server. Document attachments are the first components to use the DAOS feature in Domino®.

In databases that use DAOS, Domino® no longer saves a separate and complete copy of every document attachment. Instead, the server saves a reference to each attached file in an internal repository, and refers to the same file from multiple documents in one or more databases on the same server. When an attached file is large and a message containing it is broadcast to thousands of users, creating a separate copy of the message for each recipient could require several gigabytes of disk space. Multiple copies of the same attachment often also proliferated in mail threads with multiple replies. With DAOS enabled, disk space usage is substantially reduced.

Attachment consolidation is not limited to mail -- it occurs as soon as an attachment is saved in any document of any database on the server where the feature is enabled. Savings can average one quarter of space consumed.

You can mark databases on a Domino® server for participation in attachment consolidation by enabling consolidation on the DAOS tab in the Server document, and ensuring that every database you want to include in consolidation has the Use Domino Attachment and Object Service advanced database property selected. DAOS also requires transaction logging to be enabled. DAOS stores a single copy of each attachment in a central mapped repository. After you enable attachment consolidation on a server, all databases on the server that are included in consolidation use the repository to store attachments.

When attachment consolidation is enabled and a user saves an attachment, the body stored in the document contains a reference, sometimes called a "ticket," to the attachment, which identifies the attachment in the repository. Consolidation occurs immediately; you do not have to wait for a task to run before disk space savings occur in the size of documents with attachments.

Administrators can use other settings on the DAOS tab to specify a minimum size that an attachment must reach before being consolidated, and to specify the parent directory on the server for the repository.

Attachment consolidation is completely transparent to users. When a recipient opens a document, the attachment icons display the same whether the document's database is on a server where consolidation is enabled or a server where it is not. Users can delete, save locally, replace, and perform any other familiar tasks with attachments. If users delete or replace an attachment, or create new documents or messages containing copies of existing attachments, the server adjusts references to each attachment in the repository as necessary, using mapping to determine which attachments on the server are identical.

When using attachment consolidation for mail files, also use it for any MAIL.BOX files on the server.

Consolidation works for all databases that have the current on-disk structure (ODS). Databases with an earlier ODS do not include the DAOS setting in advanced properties, but you can pre-enable them for consolidation in the Domino® Administrator client so that they are included in consolidation when later upgraded to the current level of ODS.