Running HPU without a QUIESCE or STOP might result in missing or incomplete data

Technote (FAQ)


Question

DB2® High Performance Unload (HPU) operates on the physical VSAM dataset level that is outside of DB2. Be careful when you use HPU without issuing a QUIESCE or STOP on the object.

Answer

If you run High Performance Unload on a table where a row was just inserted, it is possible that the unloaded data might not contain the row that was inserted.

The unloaded data does not show the row because DB2 might not have externalized the data to DASD yet. Because HPU operates on the physical VSAM dataset level, some rows could be missing. A program that works only at the VSAM level does not have access to changes that might still reside in the DB2 buffer pool, but have not yet been externalized to DASD.

To prevent this, use the QUIESCE YES parameter, or STOP the object.

While QUIESCE is a possible solution, it causes the buffers to be externalized, which means that immediately afterwards another application might cause an update to the data.

On the other hand, if you issue a STOP of the object, it guarantees that no updates will occur between actions.

If availability is an issue, you might consider generating the UNLOAD from an image copy.


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Document information


More support for:

DB2 Tools for z/OS
DB2 High Performance Unload

Software version:

1.1.0, 1.2.0, 2.1.0

Operating system(s):

OS/390, z/OS, zSeries

Reference #:

1046493

Modified date:

2003-03-04

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