Syntax options:

    SNAPSHOT IS ENABLED IMMEDIATE | SNAPSHOT IS ENABLED DEFERRED

    Specifies when read/write transactions write database changes
    they make to the snapshot file used by read-only transactions.

    The default is ENABLED IMMEDIATE and causes read/write
    transactions to write copies of rows they modify to the snapshot
    file, regardless of whether or not a read-only transaction is
    active.

    The ENABLED DEFERRED option lets read/write transactions
    avoid writing copies of rows they modify to the snapshot file
    (unless a read-only transaction is already active). Deferring
    snapshot writing in this manner improves the performance for
    the read/write transaction. However, read-only transactions that
    attempt to start after an active read/write transaction starts
    must wait for all active read/write users to complete their
    transactions.