使用dbca建庫時遇到ORA-01501: CREATE DATABASE failed這個錯誤，檢查告警日志，發現有下面錯誤信息：
SMON: enabling tx recovery
Fri Apr 29 14:06:25 HKT 2016
replication_dependency_tracking turned off (no async multimaster replication found)
Starting background process QMNC
Process QMNC died, see its trace file
Fri Apr 29 14:06:26 HKT 2016
Errors in file /u01/app/oracle/admin/EPPS/udump/epps_ora_6832.trc:
ORA-00444: background process "QMNC" failed while starting
ORA-00020: maximum number of processes () exceeded
Fri Apr 29 14:06:26 HKT 2016
Errors in file /u01/app/oracle/admin/EPPS/udump/epps_ora_6832.trc:
ORA-01501: CREATE DATABASE failed
ORA-00450: background process 'QMNC' did not start
ORA-00444: background process "QMNC" failed while starting
ORA-00020: maximum number of processes () exceeded
Error 450 happened during db open, shutting down database
USER: terminating instance due to error 450
Instance terminated by USER, pid = 6832
ORA-1092 signalled during: CREATE DATABASE "EPPS"
從錯誤信息看，后台進程"QMNC"沒有啟動，后台進程"QMNC"啟動失敗，檢查對應的跟蹤文件，發現ORA-00020: maximum number of processes () exceeded，也就是說因為processes超了，導致后台進程無法啟動。
仔細檢查后，發現我設置的參數process的值為150，但是在連接模式（Connection Mode）里給了Shared Servrer給了一個很大的值（當時一邊操作，一邊接電話，把這個值誤當成session的值），所以導致后面一系列錯誤。重新正確設置Shared Servrer值，然后用DBCA建庫，問題解決！