Shulou(Shulou.com)06/02 Report--

DCD: Dead Connection Detection, which can be used to detect, mark dead and not disconnected session, and then cleaned up by PMON to release resources.

To enable DCD, you only need to add SQLNET.EXPIRE_TIME parameter to sqlnet.ora file on server side, unit is minutes:

SQLNET.EXPIRE_TIME = 10

If the time reaches this value, the server sends a "probe" packet to the client. If the client is interrupted normally, this packet is ignored and the timer restarts. If the client is interrupted abnormally, the server receives a message to release the connection.

DCD can also be used to prevent firewall timeout, for example:

A backup of a system RMAN ends with:

released channel: dev_0released channel: dev_1released channel: dev_2released channel: dev_3released channel: dev_4released channel: dev_5released channel: dev_6released channel: dev_7released channel: dev_8released channel: dev_9released channel: dev_10released channel: dev_11RMAN-00571: ===========================================================RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============RMAN-00571: ===========================================================RMAN-06004: ORACLE error from recovery catalog database: ORA-03135: connection lost contactORACLE error from recovery catalog database: ORA-03114: not connected to ORACLE

Reference article (ID 729811.1):

+ Is the rman catalog Database running on a different system than the Target Database? If so, verify with the System Administrators what the TCP/IP timeout is set to.If there is any firewall between two systems, set the value of SQLNET.EXPIRE_TIME to less than the TCP timeout value of the firewall. + Increase the value of SQLNET.EXPIRE_TIME in the sqlnet.ora file on both target servers if no firewall exists between two systems. + Increase the value of keepalive interval.

The above example of RMAN error is due to firewall timeout setting. When there is no data transmission between client and server within timeout time, the session will be disconnected by firewall. This can be avoided by setting the SQLNET.EXPIRE_TIME parameter to be less than the firewall timeout time.

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