現有兩個資料庫,自己的資料庫,別人的資料庫

        近期一個功能上線之後,對方的開發人員經常過來抱怨說,他們的資料庫連線數超了,導致

連不上，由於我們的新功能是通過dblink從我們資料庫到他們資料庫查資料，所以他們懷疑是我們資料庫的連線沒關，排查後發現程式碼裡面有關閉連線，沒問題。

後來查閱發現，資料庫通過dblink查詢，會開啟一個session，即使是select也會，附上別人查閱的官方文件

Managing a Distributed Database

Closing Database Links

If you access a database link in a session, then the link remains open until you close the session. A link is open in the sense that a process is active on each of the remote databases accessed through the link. This situation has the following consequences:

• If 20 users open sessions and access the same public link in a local database, then 20 database link connections are open.

• If 20 users open sessions and each user accesses a private link, then 20 database link connections are open.

• If one user starts a session and accesses 20 different links, then 20 database link connections are open.

After you close a session, the links that were active in the session are automatically closed. You may have occasion to close the link manually. For example, close links when:

• The network connection established by a link is used infrequently in an application.

• The user session must be terminated.

To close a link, issue the following statement, where linkname

ALTER SESSION CLOSE DATABASE LINK linkname;

Note that this statement only closes the links that are active in your current session.

解決：

    我們是通過was連線池取的連線，即使程式程式裡面把連線close了，也只是把連線放回was的連線池，但是session還在，所以連線一隻佔著導致別人的資料庫連線數超了。所以用dblink的時候，就算是select操作，也在後面加上con.commit或者con.rollback