PowerExchange Interfaces for PowerCenter

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Connection Attributes for CDC Commit Processing

The following table describes the optional CDC connection attributes that you can use to control target commit processing:

Connection Attribute	Real Time or Change	Description
Maximum Rows Per commit	Both	The maximum number of change records that PWXPC processes before it sends a commit request to PowerCenter to commit data to all targets in the CDC session. PWXPC does not wait for a UOW boundary to commit the change data. Default is 0, which disables this attribute.
Minimum Rows Per commit	Real Time	The minimum number of change records that PowerExchange must read from the change stream before it can pass any source commit record to PWXPC. Before reaching this minimum, PowerExchange passes only the change records, without any commit records, to PWXPC. Default is 0, which disables this attribute.
Real-time Flush Latency in milli-seconds	Real Time	The number of milliseconds that must elapse before PWXPC sends a commit request to PowerCenter. When this period elapses, PWXPC continues to read the changes in the current UOW until it reaches the end of the UOW. Then PWXPC sends a commit request to PowerCenter so that the data can be committed to the targets. Valid values: -1 . Disables this attribute. 0 to 86400 . Specifies the number of milliseconds that must elapse before PWXPC sends a commit request to PowerCenter. If you specify a value from 0 through 2000, PWXPC uses 2000 milliseconds (2 seconds). Default is 0.
UOW Count	Both	The number of UOWs that PWXPC processes before it sends a commit request to PowerCenter to commit data to all targets in the CDC session. Valid values: -1 . Disables this attribute. 0 . Disables this attribute. n . Specifies the number of UOWs that PWXPC processes before sending a commit request. Default is 1.

You can specify values for all of these commit control attributes. However, PWXPC flushes the data buffer to commit change data to the targets only when one of the following attribute values is met, whichever is first:

Maximum Rows Per commit

Real-time Flush Latency

UOW Count

After PWXPC commits the change data, it resets the

Maximum Rows Per commit

Real-time Flush Latency

, and

UOW Count

counters and continues to read change data. When one of these commit-control attribute values is met again, PWXPC commits the new change data to the targets. Commit processing continues until the CDC session is stopped, ends normally, or ends abnormally. When the PWXPC CDC reader ends normally, PWXPC issues a final commit to flush all of the complete, buffered UOWs and their final restart tokens to the targets. Before ending, the PWXPC CDC reader writes the following message to the session log:

PWXPC_12075 [INFO] [CDCRestart] Session complete. Next session will restart at:  Restart 1 [restart1_token] : Restart 2 [restart2_token]

If you select the

Commit On End Of File

property on the session

Properties

tab, duplicate data might occur on the targets because the PowerCenter Integration Service commits any remaining change data in the buffer to the targets. This final commit occurs after the PWXPC CDC reader has committed all complete UOWs in the buffer, along with their restart tokens, to the targets. As a result, the restart tokens might represent a point in the change stream that is earlier than final change data that the PowerCenter Integration Service commits to the targets. To prevent possible duplicate data when you restart CDC sessions, set the

Commit Type

session property to

Source

and clear the

Commit On End Of File

property.

Configuring Connection Attributes

Target Latency

Commit Processing for CDC Sessions

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