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-24404: connection pool does not exist
文档解释ORA-24404:connectionpooldoesnotexistCause:Anattemptwasmadetousetheconnectionpoolbeforecreatingit.Action:Createtheconnectionpool.ORA-24404：连接池不存在官方解释ORA-2440...
ORA-24392: no connection pool to associate server handle
文档解释ORA-24392:noconnectionpooltoassociateserverhandleCause:OCIServerAttachcalledinOCI_POOLmodebutnoconnectionpoolfoundtoassociatetheserverhandle.Action:1)Verify...
ORA-30678: too many open connections
文档解释ORA-30678:toomanyopenconnectionsCause:Anattempttoopenaconnectionfailedbecausetoomanyarealreadyopenbythissession.Thenumberofallowedconnectionsvariesassomemay...
ORA-44827: Number of Performance Classes is too large
文档解释ORA-44827:NumberofPerformanceClassesistoolargeCause:Alargenumber(>=50)ofPerformanceClasseswererequested.Action:Submitasmaller(ORA-44827：表示性能类的数量太多。官方解释OR...