Changes

Each database has its own queue: An update on database A will not block operations on database B. This is under the premise that it can be statically determined, i.e., before the transaction is evaluated) , which databases will be accessed by a transaction (see [[#Limitations|below]]). The number of maximum parallel transactions can be adjusted with the [[Options#PARALLEL|PARALLEL]] option.

* Jobs without database access will never be locked. Globally locking jobs can now be executed in parallel with non-locking jobs.* A {{Option|FAIRLOCK}} option has been added: By default, which is now false by default: Read read transactions will now be favored, and transactions that access no databases can be evaluated even if the maximum transactions limit has been reached.* A globally locking job can now be executed in parallel with a non-locking job.

==External Side EffectsXQuery Locks==

Access By default, access to external resources (files on hard disk, HTTP requests, ...) is not controlled by the transaction monitor of BaseX unless specified by the user.You can use custom XQuery locks to do so:

===XQuery Locking Query Options===

Custom * You can declare custom locks can be acquired by setting via the BaseX-specific XQuery options {{Code|query:read-lock}} and {{Code|query:write-lock}}. Multiple option declarations may occur options in the query prolog .* The value of a querythe option contains the lock string, but or multiple values can also be ones (separated with commas in a single declaration). These locks are in another namespace than * Similar to the internal database names: the lock value {{Code|factbook}} locks, write locks block all other operations while read locks allow parallel access.* The internal locks and XQuery locks can co-exist (there will not be no conflicts, even if your lock string equals the name of a database named factbookthat will be locked by the transaction manager).

These option declarations will put read In the following two example modules, locks on ''foo'', ''bar'' and ''batz'' and a have been added to prevent concurrent write lock operations on ''quix''the same file:

module namespace read = 'read'; (:~ Read lock on CONFIG key. :)declare option query:read-lock "foo,bar"'CONFIG'; declare option queryfunction read:config() { file:read-lock text('config.txt')};</pre> <pre class="batzbrush:xquery">module namespace write = 'write'; (:~ Write lock on CONFIG key. :)declare option query:write-lock "quix"'CONFIG'; declare function write:file($data) { file:write-text('config.txt', $data)};