SQLNET.EXPIRE_TIME參數(shù)—之防火墻短連接

發(fā)布時(shí)間：2020-08-11 03:53:15 來源：ITPUB博客閱讀：1060 作者：swq618 欄目：建站服務(wù)器

DCD: Dead Connection Detection ，可以用于檢測(cè)、標(biāo)記僵死而沒有斷開會(huì)session，再由PMON進(jìn)行清理，釋放資源。
開啟DCD，只需要在服務(wù)端的sqlnet.ora文件中添加SQLNET.EXPIRE_TIME參數(shù)，單位為分鐘：

SQLNET.EXPIRE_TIME = 10

如果時(shí)間達(dá)到這個(gè)值，server端就是發(fā)出一個(gè)”probe” packet 給客戶端，如要客戶斷是正常的，這個(gè)packet就被忽略，timer重新計(jì)時(shí)；如果客戶端異常中斷，則server端就會(huì)收到一個(gè)消息，用以釋放連接。

DCD還可以用于防止防火墻的timeout，例如：

某個(gè)系統(tǒng)RMAN備份，在結(jié)束時(shí)，報(bào)：

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RMAN-00571: ===========================================================

RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============

RMAN-00571: ===========================================================

RMAN-06004: ORACLE error from recovery catalog database:

ORA-03135: connection lost contact
ORACLE error from recovery catalog database:

ORA-03114: not connected to ORACLE

參考文章(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.

以上這個(gè)RMAN報(bào)錯(cuò)例子就是由于防火墻設(shè)置timeout原因，當(dāng)client和server在timeout時(shí)間內(nèi)沒有數(shù)據(jù)傳輸?shù)臅r(shí)候，會(huì)話就會(huì)被防火墻斷開。而設(shè)置SQLNET.EXPIRE_TIME參數(shù)，使其小于防火墻的timeout時(shí)間，就可以避免這一情況的發(fā)生。

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SQLNET.EXPIRE_TIME參數(shù)—之防火墻短連接

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