Dead connection detection ( DCD ) is a Oracle net feature which is primarily intended for environments where clients power down their systems or client machine crashes unexpectedly without gracefully closing the connections from the Oracle database.

In cases where client machine abruptly crashes with properly disconnection the sessions from Oracle databases the resources locked by such sessions continue to be locked thereby causing performance issues in the environment. Since this scenario can occur in any environment Oracle net service came up with the feature of DCD to detect such scenarios in early stage which enables speedy recovery of the locked resources.

To resolve this situation and to detect the dead connections Oracle introduced a new concept at the network session (tcp in 12c) layer. Server process sends SQL*Net Probe packets to the client to check if the connection is still usable in every fixed interval of time which is specified by sqlnet.expire_time parameter. If this communication via probe packets is failed an error is returned which causes the server process to exit.

When the application is not used for a significant amount of time, the firewall setting between database & application server closes physical connection between application & database.

This will invalidate the connection in connection pool. To detect such dead connections we can make use of EXPIRE_TIME parameter.

So if the value of this parameter is specified as 1, sqlnet will send a probe after every 1 minute to check the connection validity. Oracle recommends setting the value of this parameter to a non-zero value.

Dead connection detection ( DCD ) is a Oracle net feature which is primarily intended for environments where clients power down their systems or client machine crashes unexpectedly without gracefully closing the connections from the Oracle database.

In cases where client machine abruptly crashes with properly disconnection the sessions from Oracle databases the resources locked by such sessions continue to be locked thereby causing performance issues in the environment. Since this scenario can occur in any environment Oracle net service came up with the feature of DCD to detect such scenarios in early stage which enables speedy recovery of the locked resources.

To resolve this situation and to detect the dead connections Oracle introduced a new concept at the network session (tcp in 12c) layer. Server process sends SQL*Net Probe packets to the client to check if the connection is still usable in every fixed interval of time which is specified by sqlnet.expire_time parameter. If this communication via probe packets is failed an error is returned which causes the server process to exit.

Dead connection detection ( DCD ) is a Oracle net feature which is primarily intended for environments where clients power down their systems or client machine crashes unexpectedly without gracefully closing the connections from the Oracle database.

In cases where client machine abruptly crashes with properly disconnection the sessions from Oracle databases the resources locked by such sessions continue to be locked thereby causing performance issues in the environment. Since this scenario can occur in any environment Oracle net service came up with the feature of DCD to detect such scenarios in early stage which enables speedy recovery of the locked resources.

To resolve this situation and to detect the dead connections Oracle introduced a new concept at the network session (tcp in 12c) layer. Server process sends SQL*Net Probe packets to the client to check if the connection is still usable in every fixed interval of time which is specified by sqlnet.expire_time parameter. If this communication via probe packets is failed an error is returned which causes the server process to exit.

When the application is not used for a significant amount of time, the firewall setting between database & application server closes physical connection between application & database.

This will invalidate the connection in connection pool. To detect such dead connections we can make use of EXPIRE_TIME parameter.

So if the value of this parameter is specified as 1, sqlnet will send a probe after every 1 minute to check the connection validity. Oracle recommends setting the value of this parameter to a non-zero value.

CAUAJM_E_18416 Event Server: <PFWLAR>  Failed Query: <BEGIN :RetVal := ujo_get_jobstart_depends_pkg.ujo_get_jobstart_depends (:I_joid, :I_cond_job_name, :I_autoserv, :I_mode, :B_dep_joid, :B_joid, :B_priority, :B_job_ver, :B_over_num, :Done); END; <<3635,'','',4>>>

There could a period of time when there is no WAAE activity / jobs being processed and that the firewall drops the database connection between Oracle and WAAE. Then WAAE attempts to start a job but realizes the database connection is dead and needs to make a new connection.

Note: WAAE (Autosys) opens persistent connections to the DB at startup.  These connections are never killed by Autosys.

Dead Connection Detection | Oracle Database Internal Mechanism


Posted by 2018 article

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