com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Data source rejected establishment of connection, message from server: Too many connections
最简单的办法是因为你的my.ini中设定的并发连接数太少或者系统繁忙导致连接数被占满解决方式：打开MySQL安装目录打开MY.INI找到max_connections默认是100.--实例WINDOWS解决mysql Errno.:1040错误XXXXinfo:CannotconnecttoMySQLserv...
hadoop中combiner是什么
Combiner（合并器）在Hadoop中，Combiner（合并器）是一个可选的阶段，用于优化MapReduce任务的性能。它是在Map阶段输出之后、规约（reduction）之前执行的。Combiner的作用是在Map任务的本地节点上对Map阶段的输出进行局部聚合。它接收Map任务输出的键值对，并将具有相同键的键值...
ORA-44747: An XMLIndex with a structured component cannot be specified with ASYNC.
文档解释ORA-44747:AnXMLIndexwithastructuredcomponentcannotbespecifiedwithASYNC.Cause:AnattemptwasmadetospecifyASYNCparameterforanXMLIndexwithastructuredcomponent.Ac...
ORA-32415: fast refreshable remote materialized view on a detail table with commit SCN-based materialized view log is not supported
文档解释ORA-32415:fastrefreshableremotematerializedviewonadetailtablewithcommitSCN-basedmaterializedviewlogisnotsupportedCause:Thematerializedviewcreationfailedbeca...
ORA-24167: incompatible rule engine objects, cannot downgrade
文档解释ORA-24167:incompatibleruleengineobjects,cannotdowngradeCause:thereareruleengineobjectsinthedatabasethatcannotbedowngraded.Action:checkutlincmp.sqlandremovea...