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Urgent from Sybase: Possible data integrity issues using Adaptive Server Enterprise 12.5.x on 32-bit Linux systems

Summary: This document describes two separate topics that may lead to data integrity issues in 32-bit Linux Adaptive Server Enterprise (ASE 12.5.x). The issues are:

  1. Use of file system devices in ASE version 12.5.3 ESD #2 in the event of a system crash.
  2. Use of Large Memory Support, a feature available in ASE 12.5.2 and higher.

Note: This risk does not apply to Linux 32-bit Express Editions (ASE 12.5.2 Linux Express Edition EBF 12123 and ASE 12.5.3 ESD #1 Linux Express Edition EBF 12406).


Contents

This document contains the following sections:

  • Customer Alert
  • Recommendation

Customer Alert

Use of file system devices in ASE 12.5.3 ESD #2

A system crash may lead to data integrity issues when using a file system for a database device on ASE 12.5.3 ESD#2 EBF 12462 running on (32-bit Linux) Red Hat Advanced Server 2.1 or Red Hat Enterprise Linux 3.0. The direct I/O request from ASE to bypass the file system cache is ignored by the operating system. ASE assumes all writes have been committed to disk, while the modified pages may be retained in the file system cache. In the event of a power failure or other system crashes, the cached modifications may be lost leading to data inconsistency.

This problem is not applicable to the direct I/O implementation in SuSE 9.0, nor is it an issue with file systems used for temporary databases as they are re-created during server reboot.

This issue is being tracked under Sybase CR 392262.

Workaround: The problem described affects only ASE 12.5.3 ESD#2. If you intend to remain on this version, you must switch your database devices to raw partitions. Otherwise, upgrade to ASE 12.5.3 ESD #3, where CR 392262 is fixed.

Symptoms: If your system has not crashed, your data is NOT affected by this issue. If your system has crashed, running DBCC CHECKSTORAGE or DBCC CHECKDB may identify any structural data inconsistencies.

Use of Large Memory Support in ASE 12.5.2 and higher

695, 697 and other data integrity errors may be reported using ASE 12.5.2 or above when a 2K-page size is being used and Large Memory Support (LMS) has been enabled. Setting the configuration parameter ?extended cache size? to a non-zero value enables LMS.

This issue is being tracked under Sybase CR 387523.

A 605 error may be reported on an OAM page. This issue is being tracked under Sybase CR 391734.

Workaround: Disable Large Memory Support by setting extended cache size to zero. To do this, execute this command:

sp_configure "extended cache size", 0


Recommendation

CRs 387523, 391734 and 392262 are fixed in ASE 12.5.3 ESD#3 (EBF 12600). Sybase recommends an upgrade to this version of ASE.

Note: Linux Express Edition releases are not affected by the above problems.

  • CRs 387523 and 391734 are related to large memory support, which is not supported on Linux Express Edition releases.
  • CR 392262 is also not applicable as the ASE 12.5.3 ESD#2 version of Express Edition is not released.

The EBF can be obtained from the Sybase EBFs and Maintenance site.

http://downloads.sybase.com/

Follow the instructions in the EBF cover letter to install the EBF.


If you require further assistance please contact your local support center. The contact numbers can be found in the About Support section under Support & Services at the www.sybase.com website.

http://www.sybase.com/contactus/support



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