最近開發組同事使用Azure的Function App訪問公司內部的Oracle數據庫時，偶爾會遇到“ORA-12537: Network Session: End of file”這個錯誤。關於ORA-12537的詳細信息如下：
[oracle@DB-Server ~]$ oerr ora 12537
12537, 00000, "TNS:connection closed"
// *Cause: "End of file" condition has been reached; partner has disconnected.
// *Action: None needed; this is an information message.
按照官方文檔，引起ORA-12537的錯誤原因很多，如下所示：
ORA-12537 is an informational message and means that the connection has been closed. This error message can happen due to any of the following reasons:
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There are too many connections being open by the application.
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There are configuration issues in the sqlnet.ora, protocol.ora and listener.ora files.
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Database is shut down (maybe for nightly backup), but connection to database was kept by client.
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A timeout occurred on the client connection.
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A firewall closed idle connections.
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There is a path name that is too long for the Oracle TNS client on Windows. See Note:263489.1
一一分析、排除后，懷疑我設定的一個定期清理超過90分鍾空閑會話的作業導致了這個問題，具體參考“ORACLE定期清理INACTIVE會話”，測試了一下，我們通過V$SESSION找到對應的會話，然后使用下面SQL終止會話。
SQL> ALTER SYSTEM DISCONNECT SESSION 'xxx,xxx' IMMEDIATE;
Azure的Function App測試驗證發現報“ORA-12537: Network Session: End of file” 。注意：ALTER SYSTEM KILL SESSION 'xxx,xxx' IMMEDIATE;也是同樣的錯誤。
但是如果你使用SQL*Plus等工具（使用SQL*Net連接數據庫），測試發現報ORA-03113：通信通道的文件結尾“，而不是ORA-12537這個錯誤，如下所示：
查了一下官方文檔關於Azure的Function（Function App）連接數據庫的相關知識，因為連接池緣故，應用程序關閉會話后，連接池對應的數據庫會話一直處於INACTIVE狀態，而當達到條件時（空閑時間超過90分鍾），就被作業清理掉，而此時如果Azure的Function應用再次訪問數據庫時，由於連接池的相關會話被清理掉了，從而報錯。