Red Alert Could Impact DB2 10 Users, z/OS 1.12 and 1.13 Releases

This IBM Red Alert notification, “Potential loss of data for DB2 v10 users on z/OS 1.12 and 1.13 releases,” is dated May 29:

                Users Affected:

                DB2 V10 and PDSE users potentially affected by error in z/OS Media Manager IO recovery. Users of zDMF running zHPF may be particularly exposed because all I/O requests are intercepted by zDMF and returned to Media Manager in error for IO redrive using FICON, however any I/O errors, including interface control check and unit checks, that are retried by the media manager are also subject to the problem.

                Description:

                There are certain situations where the Media Manager will redrive the failed channel program with a different type of channel program. In some highly timing dependant cases, such as with I/Os that cross extents, the redrive may not occur correctly, and no error is presented to the caller, potentially leading to data being down level on disk. The problem may occur for DB2 V10 or PDSE data sets. Please see APAR OA42277 for more details.

                Recommended Actions:

                Apply ++APAR or PTFs for OA42277. Activation requires re-IPL of the system.

                Also please do not use zDMF until the fix for OA42277 is applied.

A May 31 update to this alert added z/OS 2.1 to the list of platforms and IMS FastPath DEDB to the list of databases impacted.

 

Red Alert: Potential data loss in DB2 10 data sharing environment

On March 25, IBM posted a Red Alert for customers running DB2 10 for z/OS data sharing environment. See this detailed description.

In summary,  PTF UK91435 must be applied as soon as possible to avoid a potential data loss. The problem occurs during data modifications with insertions and mass deletes. The data may not be recoverable using standard recovery procedures. However, the changes are recorded to the DB2 log, so a log analyzer tool can be used to rebuild the redo statements.

The best way to determine if you have a problem is to run the CHECK INDEX or CHECK DATA utilities. Any issues uncovered should be reported to IBM Software Support to determine root cause.

Additional information can be found in APAR PM79520.

 

DB2 10 Data Sharing Fix Issued

IBM recently released a Red Alert for customers who are using data sharing and DB2 10 for z/OS.
Fortunately we don't see these very often. When they are issued they should be taken very seriously. From the alert:

"IBM has become aware of potential data loss when running data sharing under any mode of DB2 10 for z/OS.

"DB2 10 for z/OS takes advantage of a CFCC/XES performance enhancement by allowing repeated READ CASTOUT CLASS requests to the CF to utilize a restart token and retrieve from the queue where the previous read left off. A defect has been identified in this implementation of the enhanced READ CASTOUT CLASS in DB2 10 for z/OS."

The alert further states that APAR PM51655 should be applied to revert the DB2 10 behavior of the READ CASTOUT CLASS to the DB2 V9 (and prior releases) behavior.

Read more about this Red Alert and the recommended action here.