The following parameters control the replication process.
Replication process available controls the replication background process on a master site. The replication background process checks the replication queue. When the background process finds a row in the replication queue it creates a Connectivity message. Connectivity sends the message to the replica(s). The process is only needed on a master site.
Replication process restartup interval (seconds) controls the replication background process interval between wake-ups of the process. The process will sleep for the specified number of seconds before checking for a new row in the replication queue.
The replication background process creates a connectivity message and place it in the connectivity outbox. The message will be processed by the connectivity outbox process. This means that the Connectivity Outbox process available parameter needs to be ON in order for connectivity to process the message.
Cleanup age limit in days for replicated messages controls the cleanup of the replication queue and the cleanup of replication messages in the connectivity outbox and inbox. The cleanup only removes rows that have been successfully processed. The value is specified in days. Fraction of days is allowed. 0.007 days equals 10 minutes.
Note: The cleanup process will also remove
successfully processed background jobs that has been processed in batch queues with
the string "replication" in the description. This may cause unexpected
removal of background jobs. Patch for bug 89177 implements a redesigned cleanup
process that will remove only background jobs initiated by the replication process.
All errors in the replication process are logged. Warnings and information can also be logged. This is controlled by the parameters Log Replication Send warnings, Log Replication Send information, Log Replication Receive warnings and Log Replication Send information. While logging can be space consuming it is recommended that the logging parameter is set to ON only in the setup and test phase.
Replication statistics can be collected. The statistics will contain the number of send and receive operations and the numbers of errors on send and receive operations. The statistics is summed up on Replication Object, Logical Unit and Date Time value.
Collect Replication statistics information controls the collection of statistics.
Replication statistics date key format controls the sum up interval for the statistics. With a value of YYYY-MM-DD statistics will be summed up daily and a value of YYYY-MM-DD-HH24 will sum up the statistics hourly.
Several processes are involved when data is replicated. The interval with which messages will be sent from a master to a replica is affected by the interval between wake-ups for several processes and by the configuration of Oracle job queue background processes (the SNP processes).
The replication background process (Replication_SYS.Process_Replicate__)
will create a background process entry in Transaction_SYS for each
row in the replication queue. This job will be executed by Transaction_SYS.Process_All_Pending__.
The wake-up interval for this process is controlled by Batch
Queue Administration. When the job (Replication_Util_API.Replicate__)
executes it will create a connectivity message. The connectivity process (Connectivity_SYS.Process_Outbox__)
will in turn create a background process entry in Transaction_SYS for
each row in the out message box. The wake-up interval for this process is controlled
by Batch Queue Administration. When the final job
(Out_Message_Util_API.Transfer_Data__) executes it will send the message.
In this processing there have been four processes with wake-up interval involved. If each has a wake-up interval of 10 seconds the total waiting time may be up to 40 seconds.
All these processes are executed by the Oracle job queue background processes. They are controlled by the initialization parameters Job_Queue_Processes and Job_Queue_Interval.
Job_Queue_Processes controls the number of processes. Each process can execute one job at a time. Default value is 0 and maximum value is 1000 for Oracle12c.