Understanding Exclusive Operations on Aggregate Storage Databases

On aggregate storage databases, multiple exclusive operations cannot be performed simultaneously on the same database. If one exclusive operation is running and a second exclusive operation is attempted simultaneously, the second operation is rejected with a message indicating that the operation cannot proceed while the first operation is in progress. For example, when performing a partial data clear on an aggregate storage database, a second partial data clear cannot run concurrently on the database, even if the operations are clearing different regions in the database. While most exclusive operations are mutually exclusive, there are some exceptions.

Exclusive operations and exceptions:

Queries are allowed to run concurrently with all exclusive operations. However, if an operation adds, changes, or removes any data in the database, the following sequence takes place at the end of the operation, when the changes are made visible to queries:

  1. Any new queries are temporarily blocked from starting (the queries wait).

  2. Existing queries finish running.

  3. Data changes from the exclusive operation are committed to the database.

  4. Queries that are waiting proceed.

Queries are never rejected or canceled because of an operation that changes data on an aggregate storage cube.