Regression starting in Version 11.1.4.4.
When performing a LOAD operation, some pages are read by Load
while bypassing the bufferpool (we refer to this as a
'direct-read'). This is common in all Load operations, and most
predominant in Load operations using INDEXING MODE REBUILD.
In v9.7 and prior releases, a consistency bit was embedded at
pre-defined intervals within data and index pages. In 9.8 and
later releases, this was replaced with a checksum field. The
purpose and differences between the consistency bit and checksum
field are beyond the scope of this APAR description.
In Db2 Version 11.1.4.4, when a Load operation performs a
direct-read of a data or index page that still contains the v9.7
consistency bit format, it may not handle the consistency bit
correctly. This will result in an in-memory page
corruption at x200 offsets within the page, which may lead to
different error symptoms. This corruption could potentially
even persist to disk if load writes the page back out (as it
does for some meta table pages).
Note, a data or index page will still contain the v9.7
consistency bit format if the table and page was created on a
9.7 or earlier release, and the data or index pages was never
previously updated (inserted/updated/deleted) in a 9.8 or later
release.
Exposure to this issue will be most common in scenarios where a
9.7 or earlier database is upgraded directly to v11.1.4.4 and
Load operations performed.
Due to the nature of data or index page corruptions, symptoms
will vary, including: the potential for Load to fail with an
unexpected error; or for the Load operation to trap (especially
during the INDEX REBUILD phase, if one exists) and bring down
the database instance; or unexpected failures or traps in the
future when these corrupt pages are accessed by non-Load
operations, such as select, insert, update, delete operations. |
