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  1. Preface
  2. Change Data Capture Introduction
  3. PowerExchange Listener
  4. PowerExchange Condense
  5. DB2 for i5/OS Change Data Capture
  6. Remote Logging of Data
  7. Introduction to Change Data Extraction
  8. Extracting Change Data
  9. Monitoring CDC Sessions
  10. Managing Change Data Extractions
  11. Tuning CDC Sessions
  12. Appendix A: DTL__CAPXTIMESTAMP Time Stamps

CDC Guide for i5/OS

CDC Guide for i5/OS

Idle Time

Idle Time

Use the
Idle Time
connection attribute to indicate whether a CDC session that uses real-time or continuous extraction mode runs continuously or shuts down after it reaches the end-of-log (EOL).
You can specify that PowerExchange wait for a certain period without change activity before shutting down.
Enter one of the following values:
  • -1. The CDC session runs continuously. PowerExchange returns an end-of-file (EOF) only when you manually stop the CDC session.
  • 0. After reaching the EOL, PowerExchange returns an EOF and the CDC session ends.
    If you want a CDC session to end periodically on an active system that is rarely idle, enter 0.
  • n
    . After reaching the EOL, PowerExchange waits the specified number of seconds,
    n
    . If PowerExchange receives no change data of interest during this time interval, PowerExchange sends an EOF to the PowerCenter Integration Service and the CDC session ends successfully.
    If you enter a low value, such as 1, the CDC session might end before PowerExchange has read all available data in the change stream.
Default is -1.
PowerExchange determines the EOL by using the current end of the change stream at the point that PowerExchange started to read the change stream. PowerExchange uses the concept of EOL because the change stream is usually not static. The actual EOL is continually moving forward. After PowerExchange reaches the EOL, it writes message PWX-09967 in the PowerExchange message log.
Often, CDC sessions that run in real-time or continuous extraction mode use the default value of -1. You can manually stop a long-running CDC session by using the PowerCenter Workflow Monitor, pmcmd commands, or the PowerExchange STOPTASK command.
If you set the
Idle Time
attribute to 0, when PowerExchange reaches the EOL, it returns an EOF to PWXPC. PWXPC and the PowerCenter Integration Service then perform the following processing:
  1. PWXPC flushes all buffered UOWs and ending restart tokens to the targets.
  2. The CDC reader ends.
  3. After the PowerCenter Integration Service finishes writing the flushed data to the targets, the writer ends.
  4. After any post-session commands and tasks run, the CDC session ends.
If you set the
Idle Time
attribute to a positive number, the following processing occurs:
  1. PowerExchange reads the change stream until it reaches EOL and then the
    Idle Time
    wait interval begins.
  2. If more data is in the change stream after the EOL, PowerExchange continues to read the change stream, looking for change data of interest to the CDC session, as follows:
    • If the idle time expires before PowerExchange reads a change record of interest for the CDC session, PowerExchange stops reading the change stream.
    • If PowerExchange reads a change record of interest to the CDC session, PowerExchange restarts the timer, passes the change data to PWXPC, and continues to read the change stream. This processing continues until the idle time expires.
  3. After the idle time expires, PowerExchange passes an EOF to PWXPC.
  4. PWXPC and the PowerCenter Integration Service perform the same processing as when the
    Idle Time
    value is 0 and the CDC session ends.
When a CDC session ends because the idle time elapsed or a PowerExchange STOPTASK command was issued, PWXPC writes the following message in the session log:
[PWXPC_10072] [INFO] [CDCDispatcher] session ended after waiting for [
idle_time
] seconds. Idle Time limit is reached
If you stop a continual CDC session with the PowerExchange STOPTASK command, PWXPC substitutes 86400 for the
idle_time
variable in the PWXPC_10072 message.
If you specify both the
Reader Time Limit
and
Idle Time
attributes, the PowerCenter Integration Service stops reading data from the source when one of these attribute conditions is met, whichever one is first. Because the reader time limit does not result in normal termination of a CDC session, Informatica recommends that you use only the idle time limit.

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