MySQL Bugs: #61538: Multiple Rollback Segments documentation in 5.5

Bug #61538	Multiple Rollback Segments documentation in 5.5
Submitted:	16 Jun 2011 15:44	Modified:	20 Jun 2011 16:15
Reporter:	Arnaud Adant	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Documentation	Severity:	S3 (Non-critical)
Version:	5.5	OS:	Any
Assigned to:	John Russell	CPU Architecture:	Any

Description:
The documentation is lacking important information to benefit from Multiple Rollback Segments during MySQL binary upgrade from 5.1 to the 5.5 version.

Some customer will miss this important feature if they forget to perform a slow shutdown as part of their upgrade procedure.

How to repeat:
see the documentation

http://dev.mysql.com/doc/refman/5.5/en/upgrading-from-previous-series.html

There is nothing about the need to perform a slow shutdown and how in case of binary upgrade.

http://dev.mysql.com/doc/innodb/1.1/en/innodb-multiple-rollback-segments.html

There is a link to the glossary for slow shutdown. It should be clarified and point at least to this page  :

http://dev.mysql.com/doc/refman/5.5/en/innodb parameters.html#sysvar_innodb_fast_shutdown

A big warning should help understand there is an important change there.

Suggested fix:
1.

http://dev.mysql.com/doc/refman/5.5/en/upgrading-from-previous-series.html

Document the multiple rollback segment change.

2.

http://dev.mysql.com/doc/innodb/1.1/en/innodb-multiple-rollback-segments.html

Warn the user and clarify what a slow shutdown means especially it can take minutes or hours to complete. This might be critical for some customers.

The slow shutdown is not needed to create the missing rollback segments either during binary upgrade or fresh upgrade.

When 5.5 is started the first time (or when the datafiles are re-created), if all these conditions are not met :

1. innodb_force_recovery has been set
2. the database was not shutdown cleanly.

This message will appear

InnoDB: 127 rollback segment(s) active.

Nothing after. There will be no way to know if there are 128 rollback segments in 5.5. 

see this bug for more information http://bugs.mysql.com/bug.php?id=61539

So with this information :

the doc needs to be updated :

Suggested fix:

1.

http://dev.mysql.com/doc/refman/5.5/en/upgrading-from-previous-series.html

Document the multiple rollback segment change.

2.

http://dev.mysql.com/doc/innodb/1.1/en/innodb-multiple-rollback-segments.html

Clarify : no slow shutdown is needed here in most cases.