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Data inconsistencies between accelerator-shadow tables and empty DB2 for z/OS tables

Technote (troubleshooting)


Problem(Abstract)

Under certain conditions, data in accelerator-shadow tables might become inconsistent with empty tables stored in DB2 for z/OS

Symptom

An affected accelerator-shadow table contains more rows than the DB2 table.

The reason is that a reload of an accelerator-shadow table from an empty DB2 table does not delete rows in the reloaded table.


Cause

An error in the accelerator server software.


Environment

You are affected by this problem only if you use version 5.1.0 of IBM DB2 Analytics Accelerator for z/OS. The problem affects the following PTF levels of version 5.1.0:

  • V5.1.0 GA
  • V5.1.0 PTF-1a
  • V5.1.0 PTF-2

Diagnosing the problem

For this problem to occur a full table reload is needed, i.e. reloading a segmented table or reloading all partitions of a partitioned table.


Example of a failing use case:
1. A table contains data in DB2 for z/OS.
2. This table is loaded on the accelerator.
3. All data is deleted from the table in DB2 for z/OS.
4. The now empty table is re-loaded on the accelerator.

At this point, the table is empty on DB2 for z/OS, but the accelerator may still contain the data loaded in step 2.


Resolving the problem

The problem can be circumvented by following these steps:

1. Remove the affected table from the accelerator.
2. Re-define the affected table on the accelerator.
3. Load the newly defined table.

This error is fixed with IBM DB2 Analytics Accelerator for z/OS V5.1.0 maintenance level PTF-3

Document information

More support for: DB2 Analytics Accelerator for z/OS

Software version: 5.1.0

Operating system(s): z/OS

Reference #: 1992053

Modified date: 16 November 2016


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