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English
  • PowerExchange for CDC and Mainframe 10.5.1
  • All Products

Table of Contents

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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

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Example of Session Recovery

Example of Session Recovery

This example describes recovery processing for a CDC session with relational targets.
Assume that you aborted the CDC session from the Workflow Monitor and then issued the Restart Task command to restart the session.
PWXPC automatically performs a recovery processing when the session warm starts and writes the following message in the session log: 
PWXPC_12092 [INFO] [CDCRestart] Warm start requested. Targets will be resynchronized automatically if required
PWXPC then reads the restart tokens from the state tables and writes message PWXPC_12060 in the session log. This message records the restart tokens for the session and its sources, for example: 
PWXPC_12060 [INFO] [CDCRestart] 

===============================
Session restart information:
===============================
Extraction Map Name            Restart Token 1                                    Restart Token 2                    Source
d1dsn8.rrtb0004_RRTB_SRC_004   00000FCA65840000000000000D2E004A00000000FFFFFFFF   C1E4E2D3404000000D21B1A500000000   GMD storage
d1dsn8.rrtb0009_RRTB_SRC_009   00000FCA65840000000000000D2E004A00000000FFFFFFFF   C1E4E2D3404000000D21B1A500000000   GMD storage
d1dsn8.rrtb0005_RRTB_SRC_005   00000FCA65840000000000000D2E004A00000000FFFFFFFF   C1E4E2D3404000000D21B1A500000000   GMD storage
d1dsn8.rrtb0006_RRTB_SRC_006   00000FCA65840000000000000D2E004A00000000FFFFFFFF   C1E4E2D3404000000D21B1A500000000   GMD storage
d1dsn8.rrtb0008_RRTB_SRC_008   00000FCA65840000000000000D2E004A00000000FFFFFFFF   C1E4E2D3404000000D21B1A500000000   GMD storage
d1dsn8.rrtb0003_RRTB_SRC_003   00000FCA65840000000000000D2E004A00000000FFFFFFFF   C1E4E2D3404000000D21B1A500000000   GMD storage
d1dsn8.rrtb0002_RRTB_SRC_002   00000FCA65840000000000000D2E004A00000000FFFFFFFF   C1E4E2D3404000000D21B1A500000000   GMD storage
d1dsn8.rrtb0001_RRTB_SRC_001   00000FCA65840000000000000D2E004A00000000FFFFFFFF   C1E4E2D3404000000D21B1A500000000   GMD storage
d1dsn8.rrtb0007_RRTB_SRC_007   00000FCA65840000000000000D2E004A00000000FFFFFFFF   C1E4E2D3404000000D21B1A500000000   GMD storage
If PWXPC detects that recovery is required, PWXPC writes message PWXPC_12069 in the session log. This message usually includes the restart tokens for both the begin-UOW and end-UOW for the oldest uncommitted UOW that PWXPC re-reads during recovery. PWXPC usually stores end-UOW restart tokens in the state table or state file. However, if you specify a
Maximum Rows Per commit
 threshold on the connection, PWXPC can commit change data and restart tokens between UOW boundaries. As a result, the restart tokens might not represent an end-UOW.
The following example PWXPC_12069 message includes “from” restart tokens that are the same as those in the example PWXPC_12060 message: 
PWXPC_12069 [INFO] [CDCRestart] Running in recovery mode. Reader will resend the oldest uncommitted UOW to resync targets: 
from:  Restart 1 [00000FCA65840000000000000D2E004A00000000FFFFFFFF] : Restart 2 [C1E4E2D3404000000D21B1A500000000] 
  to:  Restart 1 [00000FCA65840000000000000D300D8000000000FFFFFFFF] : Restart 2 [C1E4E2D3404000000D21B1A500000000].
Because this session specifies a maximum rows threshold, the restart token values in the Restart 2 fields in both the “from” and “to” restart tokens is the begin-UOW value. The sequence token values in the Restart 1 fields represent the start and end change records in the UOW that is displayed in the Restart 2 field.
During recovery processing, PWXPC reads the change data records between the restart points that are defined by the two restart token values in the PWXPC_12069 message. Then PWXPC issues a commit for the change data and restart tokens. The PowerCenter Integration Service writes the change data to the target tables and writes the restart tokens to the state table. Then the session ends.
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