ORA-12516: TNS:listener could not find available handler with matching protocol stack

ORA-12516: TNS:listener could not find available handler with matching protocol stack
ORA-12516: TNS监听程序找不到符合协议堆栈要求的可用处理程序

sqlplus / as sysdba;

查看process和session的参数值和占用值
show parameter processes;
//查看processes数
select count(*) from v$process;
//查看当前占用的processes数
alter system set processes=1000 scope=spfile;
alter system set sessions=1105 scope=spfile;
根据ORACLE官方文档要求：
sessions=processes1.1+5

关闭oracle

shutdown immediate;

启动oracle
startup