Extracts

An extract is created from an existing database. Extracts can only be created from multi-write databases, and all extracts are themselves multi-write. The user can create Extract Databases (DBs) from any type of database that can be multi-write, that is DESI, PADD, CATA, ISOD, SCHE and MANU databases.

• The user cannot create extracts from foreign DBs.

• The user cannot create extracts from copy DBs.

  An extract can be worked on by one user at the same time as another user is working on the primary DB or another extract. When a user works on the extract, elements are claimed to the extract in a similar way to simple multi-write databases, so no other user can work on them.

When an extract user does a SAVEWORK, the changed data will be saved to the extract. The unchanged data will still be read via pointers back to the primary DB. When appropriate, the changes made to the extract can be issued, that is, written back to the parent database, or aborted (dropped), which means they will be deleted from the extract. Also, the extract can be refreshed, that is, updated with changes made to the parent only (which itself may actually have been made in another extract). Alternatively, an extract can be fully refreshed, that is, updated with changes made from all its extract ancestors.