If the session is not making a SQL call to Oracle (is INACTIVE) when it is terminated, the ORA-28 message is not returned immediately. The message is not returned until the user subsequently attempts to use the terminated session. When an inactive session has been terminated, STATUS in the view V$SESSION is "KILLED." The row for the terminated session is removed from V$SESSION after the user attempts to use the session again and receives the ORA-28 message. If an active session cannot be interrupted (for example, it is performing network I/O or rolling back a transaction), the session cannot be terminated until the operation completes. In this case, the session holds all resources until it is terminated. Additionally, the session that issues the ALTER SYSTEM statement to terminate a session waits up to 60 seconds for the session to be terminated; if the operation that cannot be interrupted continues past one minute, the issuer of the ALTER SYSTEM statement receives a message indicating that the session has been "marked" to be terminated. A session marked to be terminated is indicated in V$SESSION with a status of "KILLED" and a server that is something other than "PSEUDO."
1、会话没有占用过多的资源，不需要释放。这种情况一旦ALTER SESSION KILLED SESSION后需要客户端再次
ERROR at line 1: ORA-00028: your session has been killed
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