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Oracle LISTENER 中各种状态信息的含义：

LSNRCTL STATUS:
READY status means that the instance can accept connections;

BLOCKED status means that the instance cannot accept connections

READY/SECONDARY status means taht this is a secondary instance in RAC primary/secondary
configuration and is ready to accept connections

UNKNOWN status means that the instance is registered statically in the listener.ora file
rather that dynamically with service registration. therefore,the status is nonknown