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Apersistent connectionallows database connections to remains open for other requestors.A persistent connection is useful for workspaces that are long-running or published using FME Server.If this parameter is not selected,the connection to the Oracle database is closed as soon as possible after data processing is complete.
On FME Desktop,a persistent connection leaves the Oracle connection open until each translation finishes or in the case of FME Server,until an engine restart.By default the engine restart is set to 100 successful or 10 failed jobs,but this can be modified by setting theMAX_TRANSACTION_RESULT_SUCCESSESparameter in the configuration.
Persistent connections are the default setting for the readers,writers,and transformers.
For a persistent connection (default),the connection will remain until the workspace translation ends or in the case of FME Server,until an engine restart.Additionally,the TCP connections by nature will hold on to any port for another 2-4 minutes after Oracle and FME have closed the connections.
A non-persistent connection is closed as soon as possible after data processing is complete.
Oracle writers will create their own second connection,while Readers and Transformers will share the first connection (if all transformers and reader/writers are set to persistent connections).
FeatureReaders / FeatureWriters use the same connections methods as readers and writers.So for purposes of persistent connections,they should be treated the same as regular readers and writers.
Child processes sent by the FME desktop from a workspaceRunner are new instances,so unlike FME Server,the child process will use new connections and not the parent's persistent connections.
Child jobs sent from FMEServerJobSubmitter will use the same instance of the engine as their parent and therefore use the parent's persistent connections.
Occasionally when there are timeouts for idle connections,a long-running query executed in a transformer downstream can cause the connection to become idle.If the reader shares a connection with the transformer it may fail due to a database or firewall timeout.In such a case you can have the reader read everything and cache it in memory with aFeatureHolderbefore the transformer starts executing.
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