Tru64 UNIX 5.1 PK2 BL3 Direct I/O ERP

TITLE: Tru64 UNIX 5.1 PK2 BL3 Direct I/O ERP
 

Copyright (c) Compaq Computer Corporation 2001.  All rights reserved.


PRODUCT:    Tru64 [R] 5.1
SOURCE:     Compaq Computer Corporation
	    Oracle

ECO INFORMATION:

     ECO Name:  QAR84601_v51_bl3.tar.Z
     ECO Kit Approximate Size:  1.3MB
     Kit Applies To:  Tru64 5.1 Patch Kit 2 (BL3) 

ECO KIT SUMMARY:

This ECO kit contains a solution, in the form of a patch, for the following
issue:

In laboratory testing, Compaq has observed that under certain circumstances, a 
possibility exists that inconsistent data may be written to disk on some 
Tru64 UNIX V5.0A and V5.1 systems running AdvFS and direct I/O.

Compaq became aware of this possibility only during laboratory testing. To our 
knowledge, no customer has experienced this problem.  Compaq is alerting 
customers to this potential problem as a precautionary measure.

The conditions under which this potential problem may occur are as follows:

- An application writes to a file using AdvFS direct I/O and the file had 
  previously been opened for normal I/O (which by default is cached); AND

- Some but not all of the pages are still resident in Unified Buffer Cache 
  (UBC) memory.

Invalid data could occur when a single direct I/O write spans multiple AdvFS 
pages, and some, but not all, of the pages are still in the UBC.  If the file 
has been opened only for direct I/O and remains open for direct I/O, the 
problem does not exist.

Applications that use direct I/O, such as Oracle, could be affected.


CONFIGURATIONS AFFECTED:

The potential problem may affect the following systems:

- Tru64 UNIX V5.0A clustered and nonclustered systems
- Tru64 UNIX V5.1 nonclustered systems only

Only V5.0A and V5.1 systems running an application that uses direct I/O could 
experience this potential problem. Any application using direct I/O must request
this feature explicitly.

The following Oracle versions use direct I/O and may therefore be affected:
- Oracle 8.1.7
- Oracle 8.1.6.3
- Oracle 8.1.6.2 with patch 1527141
- Oracle 8.0.6.2 with patch 1523186
- Oracle 7.3.4.5 with patch 1523179

AND

the AdvFS filesystem is used for any of the following Oracle files:
- control file
- data file
- log file

An Oracle environment meeting the above criteria could experience this potential
problem. 

Oracle running on raw partitions exclusively or running LSM on raw partitions 
exclusively are not affected.

Some customers write their own applications that use direct I/O.  These 
customers should be aware of the detailed circumstances under which this 
problem could occur. The problem could occur when:

- The write spans multiple AdvFS 8K pages;
- The last page to be written is in the UBC;
- One or more of the preceding pages are not in the UBC; and
- The write to the last page is less than a full page size (8K).

Under these circumstances, the data written at the start of the total write is 
the original data, offset by the amount of data written to the last page.


PROBLEM SYMPTOM:

If Oracle customers are running one of the affected Oracle configurations, 
Oracle may have already detected an inconsistency in the database and reported 
errors similar to the following in the alert log and trace file:

  ORA-01578: ORACLE data block corrupted (file # 1, block # 100)
  ORA-01119: data file 1: '/scratch/820/qa/dbs/t_db1.f'

or

  ORA-00368: checksum error in redo block
  ORA-00354: Log corruption near block #231

Oracle customers that have run the dbverify (dbv) utility may have encountered 
an error message similar to the following:

  ***
  Corrupt block relative dba: 0x0040900b (file 0, block 36875)
  Bad header found during dbv:
  Data in bad block -
   type: 27 format: 2 rdba: 0x0040900d
   last change scn: 0x0000.0001349a seq: 0x2 flg: 0x04
   consistency value in tail: 0x349a1b02
   check value in block header: 0xa377, computed block checksum: 0x0
   spare1: 0x0, spare2: 0x0, spare3: 0x0
  ***


INSTALLATION NOTES:

Copy the ECO kit to the target system. Unzip the file using gunzip.

The patch is installed manually using the installation instructions included
in the README contained in the ECO kit. Please read through the instructions
prior to installing patches on your system.

Installation of this ECO kit requires Tru64 UNIX 5.1 and Tru64 UNIX Patch 
Kit 2 (BL3) be installed.


SUPERSEDED PATCH LIST:

None.


KNOWN PROBLEMS WITH THE PATCH KIT:

None.


[R] UNIX is a registered trademark in the United States and other countries
licensed exclusively through X/Open Company Limited.

Copyright Compaq Computer Corporation 2001.  All Rights reserved.

  This software is proprietary to and embodies the confidential technology
  of Compaq Computer Corporation.  Possession, use, or copying of this
  software and media is authorized only pursuant to a valid written license
  from Compaq or an authorized sublicensor.

       This ECO has not been through an exhaustive field test process.
       Due to the experimental stage of this ECO/workaround, Compaq
       makes no representations regarding its use or performance. The
       customer shall have the sole responsibility for adequate protection
       and back-up data used in conjunction with this ECO/workaround.

Colorado Site
Georgia Site

qar84601_v51_bl3.README
qar84601_v51_bl3.CHKSUM
qar84601_v51_bl3.tar.gz