MarkLogic 9 Product Documentation

admin:appserver-set-multi-version-concurrency-control

admin:appserver-set-multi-version-concurrency-control(
   $config as element(configuration),
   $appserver-id as xs:unsignedLong,
   $value as xs:string
) as element(configuration)

Summary

This function sets the multi version concurrency control value in the configuration for this App Server. This option specifies how the latest timestamp is chosen for lock-free queries.
When set to contemporaneous, the server chooses the latest timestamp for which any transaction is known to have committed, even though there still may be other transactions for that timestamp that have not yet fully committed. Queries will see more timely results, but may block waiting for contemporaneous transactions to fully commit.
When set to nonblocking, the server chooses the latest timestamp for which all transactions are known to have committed, even though there may be a later timestamp for which another transaction has committed. Queries won't block waiting for transactions, but they may see less timely results.

Required Privileges

http://marklogic.com/xdmp/privileges/admin/app-server

http://marklogic.com/xdmp/privileges/admin/app-server/{id}

http://marklogic.com/xdmp/privileges/admin/group

http://marklogic.com/xdmp/privileges/admin/group/{id}

Example

  xquery version "1.0-ml";

  import module namespace admin = "http://marklogic.com/xdmp/admin"
		  at "/MarkLogic/admin.xqy";

  let $config := admin:get-configuration()
  let $groupid := admin:group-get-id($config, "Default")
  return
  admin:appserver-set-multi-version-concurrency-control($config,
         admin:appserver-get-id($config, $groupid, "myAppServer"),
         "nonblocking")

  (: returns the new configuration element -- use admin:save-configuration
     to save the changes to the configuration or pass the configuration
     to other Admin API functions to make other changes.  :)