Note: This documentation is for Moodle 2.7. For up-to-date documentation see Upgrading.

Upgrading: Difference between revisions

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===Themes===
===Themes===


All core themes, except clean, have been removed from Moodle 2.7. Thus sites using any core theme (including sites using a core theme as a parent theme) other than clean must do the following:
All standard themes present in Moodle 2.6 (and earlier), except the Clean theme, have been removed from Moodle 2.7 (see MDL-43784). Custom themes and themes from the Plugins Directory are not affected, unless they use one of the removed themes as a parent theme. If a theme that was in use has been removed, the theme will revert to the new default theme called Clean.


# Download the 2.7 version of your theme as a zip file from the [https://moodle.org/plugins/browse.php?list=category&id=3 Themes section of the Moodle plugins directory].
For sites wishing to continue using any of the removed standard themes (or themes relying on a standard theme as a parent theme), other than Clean, we recommend you use the following process.
# Follow the steps above to install the new Moodle software. In step 4, unzip the theme and copy it to moodle/theme/.
 
# Download the 2.7 version of Moodle, but do not run the upgrade yet.
# Download the 2.7 version of your theme from the [https://moodle.org/plugins/browse.php?list=category&id=3 Themes section of the Moodle plugins directory] (or from the links below) into moodle/theme/.
# Proceed with the upgrade.
# Proceed with the upgrade.


Note: Only installed add-on themes may be updated automatically during the upgrade, NOT core themes. Because core themes have been removed from Moodle 2.7, they have to be re-added.
It is possible to copy missing themes into Moodle after the upgrade, but this should happen before users touch the system, otherwise theme-related settings may be lost.


===Questions===
The affected themes (with download links) are...


This problem almost certainly does not affect you.
{|-
| Afterburner
| [https://moodle.org/plugins/view.php?plugin=theme_afterburner plugins db]
| [https://github.com/moodlehq/moodle-theme_afterburner github]
|-
| Anomaly
| [https://moodle.org/plugins/view.php?plugin=theme_anomaly plugins db]
| [https://github.com/moodlehq/moodle-theme_anomaly github]
|-
| Arialist
| [https://moodle.org/plugins/view.php?plugin=theme_arialist plugins db]
| [https://github.com/moodlehq/moodle-theme_arialist github]
|-
| Binarius
| [https://moodle.org/plugins/view.php?plugin=theme_binarius plugins db]
| [https://github.com/moodlehq/moodle-theme_binarius github]
|-
| Boxxie
| [https://moodle.org/plugins/view.php?plugin=theme_boxxie plugins db]
| [https://github.com/moodlehq/moodle-theme_boxxie github]
|-
| Brick
| [https://moodle.org/plugins/view.php?plugin=theme_brick plugins db]
| [https://github.com/moodlehq/moodle-theme_brick github]
|-
| Formal White
| [https://moodle.org/plugins/view.php?plugin=theme_formal_white plugins db]
| [https://github.com/andreabix/moodle-theme_formal_white github]
|-
| Form Factor
| [https://moodle.org/plugins/view.php?plugin=theme_formfactor plugins db]
| [https://github.com/moodlehq/moodle-theme_formfactor github]
|-
| Fusion
| [https://moodle.org/plugins/view.php?plugin=theme_fusion plugins db]
| [https://github.com/moodlehq/moodle-theme_fusion github]
|-
| Leatherbound
| [https://moodle.org/plugins/view.php?plugin=theme_leatherbound plugins db]
| [https://github.com/moodlehq/moodle-theme_leatherbound github]
|-
| Magazine
| [https://moodle.org/plugins/view.php?plugin=theme_magazine plugins db]
| [https://github.com/moodlehq/moodle-theme_magazine github]
|-
| Nimble
| [https://moodle.org/plugins/view.php?plugin=theme_nimble plugins db]
| [https://github.com/moodlehq/moodle-theme_nimble github]
|-
| Nonzero
| [https://moodle.org/plugins/view.php?plugin=theme_nonzero plugins db]
| [https://github.com/moodlehq/moodle-theme_nonzero github]
|-
| Overlay
| [https://moodle.org/plugins/view.php?plugin=theme_overlay plugins db]
| [https://github.com/moodlehq/moodle-theme_overlay github]
|-
| Serenity
| [https://moodle.org/plugins/view.php?plugin=theme_serenity plugins db]
| [https://github.com/moodlehq/moodle-theme_serenity github]
|-
| Sky High
| [https://moodle.org/plugins/view.php?plugin=theme_sky_high plugins db]
| [https://github.com/moodlehq/moodle-theme_sky_high github]
|-
| Splash
| [https://moodle.org/plugins/view.php?plugin=theme_splash plugins db]
| [https://github.com/moodlehq/moodle-theme_splash github]
|-
| Standard
| [https://moodle.org/plugins/view.php?plugin=theme_standard plugins db]
| [https://github.com/moodlehq/moodle-theme_standard github]
|-
| Standard old
| [https://moodle.org/plugins/view.php?plugin=theme_standardold plugins db]
| [https://github.com/moodlehq/moodle-theme_standardold github]
|}


You can tell if you need to worry about this by looking at the bottom of the [[Environment]] check page in your site. If there is not a row mentioning questions, you don't have a problem. If there is a message about questions there, you need to do something. (This only works if you are running a version 2.4.9, 2.5.5 or 2.6.2 or later.)
Note: Only installed additional themes are updated automatically during the upgrade, NOT standard themes. Because standard themes have been removed from Moodle 2.7, they have to be re-added.


To give the background: In Moodle 2.1 there was a major upgrade to questions. As explained in [https://docs.moodle.org/21/en/Upgrading_to_Moodle_2.1#Planning_the_question_engine_upgrade the upgrade documentation for that version], it was possible to delay parts of the database upgrade to be run later. Before you upgrade to Moodle 2.7, this upgrade must be completed.
===Questions engine upgrade===
 
In Moodle 2.1, there was a major overhaul of the Question engine. As explained in [https://docs.moodle.org/21/en/Upgrading_to_Moodle_2.1#Planning_the_question_engine_upgrade the upgrade documentation for that version], it was possible to delay parts of the database upgrade to be run later. Before you upgrade to Moodle 2.7, this upgrade must be completed.
 
This will affect you if...
* your site started off on a version of Moodle 2.0.x and
* when you upgraded to Moodle 2.1 or 2.2, you made use of the complex facility to delay part of the question engine upgrade (as explained in [https://docs.moodle.org/21/en/Upgrading_to_Moodle_2.1#Planning_the_question_engine_upgrade the upgrade documentation for that version]) and
* you still have not completing that upgrade
...then you must complete it before upgrading to Moodle 2.7.
 
You can check by looking at the bottom of the [[:en:Environment|Environment]] page in your site, providing you are running a version later than 2.4.9, 2.5.5 or 2.6.2. If you have a problem, it will tell you there. If there is no mention of questions there, you can forget about this.
 
This is unlikely to affect most users.


== Backup important data ==
== Backup important data ==
Line 42: Line 132:
Before you begin upgrading your site, you should put it into [[Maintenance_mode | maintenance mode]] to stop any non-admin users from logging in.
Before you begin upgrading your site, you should put it into [[Maintenance_mode | maintenance mode]] to stop any non-admin users from logging in.


== Check for add-on updates ==
== Check for plugin updates ==


If you have [[Automatic updates deployment]] enabled, you will be able to update installed add-ons automatically during the upgrade. Just make sure you check for available updates (via the button for it) at the Plugins check screen.
If you have [[Automatic updates deployment]] enabled, you will be able to update installed plugins automatically during the upgrade. Just make sure you check for available updates (via the button for it) at the Plugins check screen.


If you are updating add-ons manually, it is a good moment now to check in the [http://moodle.org/plugins Moodle Plugins directory] whether there is a 2.7 version available for any add-ons (including themes) that you have previously installed on your site. If so, download the add-on package. In the next step, you will copy it to the appropriate location in your Moodle code (see [[Installing add-ons]]).
If you are updating plugins manually, it is a good moment now to check in the [http://moodle.org/plugins Moodle Plugins directory] whether there is a 2.7 version available for any plugins (including themes) that you have previously installed on your site. If so, download the plugin package. In the next step, you will copy it to the appropriate location in your Moodle code (see [[Installing plugins]]).


The upgrade of the add-on will then happen as part of the Moodle upgrade process.
The upgrade of the plugin will then happen as part of the Moodle upgrade process.


If an out-of-date add-on causes your upgrade to fail, you can usually delete the add-on code rather than uninstalling it from within Moodle so that the data associated with it is not deleted.
If an out-of-date plugin causes your upgrade to fail, you can usually delete the plugin code rather than uninstalling it from within Moodle so that the data associated with it is not deleted.


== Install the new Moodle software ==
== Install the new Moodle software ==
Line 59: Line 149:
# Unzip or unpack the upgrade file so that all the new Moodle software program files are in the location the old files used to be in on the server. Moodle will adjust SQL and moodledata if it needs to in the upgrade.
# Unzip or unpack the upgrade file so that all the new Moodle software program files are in the location the old files used to be in on the server. Moodle will adjust SQL and moodledata if it needs to in the upgrade.
# Copy your old [[Configuration file|config.php file]] back to the new Moodle directory.  
# Copy your old [[Configuration file|config.php file]] back to the new Moodle directory.  
# As mentioned above, if you had installed any custom add-ons on your site you should add them to the new code tree now. It is important to check that you get the correct version for your new version of Moodle. Be particularly careful that you do not overwrite any code in the new version of Moodle.
# As mentioned above, if you had installed any plugins on your site you should add them to the new code tree now. It is important to check that you get the correct version for your new version of Moodle. Be particularly careful that you do not overwrite any code in the new version of Moodle.
# Dont forget to also copy over your moodledata folder / directory.  If you don't you will get a "fatal error $cfg- dataroot is not configured properly".
# Dont forget to also copy over your moodledata folder / directory.  If you don't you will get a "fatal error $cfg- dataroot is not configured properly".


Line 107: Line 197:


The config.php file from your installation should work fine but if you take a look at config-dist.php that came with Moodle 2.7 there are more/different options available (e.g. database drivers and settings). It's a good idea to map your old config.php settings to a new one based on the 2.7 config-dist.php.
The config.php file from your installation should work fine but if you take a look at config-dist.php that came with Moodle 2.7 there are more/different options available (e.g. database drivers and settings). It's a good idea to map your old config.php settings to a new one based on the 2.7 config-dist.php.
===Cron===
Cron has received a major update (MDL-25499) and now has support for both scheduled and adhoc tasks.
The benefits of these changes are:
* The schedule for every task can be configured by the admin
* Tasks can run in parallel
* Cron processes use locking to prevent the same task running at the same time by different processes
* Clusters with multiple identical application nodes are supported, you can run cron on all of them
A result of this is that cron can be run much more often, which means (for example) forum posts can be sent out sooner.  To take advantage of the new cron system it is now strongly recommended that administrators increase the frequency that cron is run to at least ''once per minute''.
You also may need to modify any automated scripts you have that are parsing the output from cron. It is no longer possible to simply monitor the output of cron for the string "Cron script completed correctly" (if that is what you were doing). An alternative is to monitor the output for the string "task failed:". If you detect that a task is failing, [[Cron#Debugging_Scheduled_Tasks|here]] are some tips for debugging the failure.
Before the upgrade to 2.7, there may have been a cron task that was failing, which was preventing the rest of cron from being executed. A failure in any single task will no longer prevent the rest of the Moodle cron tasks from executing, so you may uncover previously masked bugs. It is a good idea to closely monitor the output from cron after the upgrade to 2.7.


===Assignments===
===Assignments===
Line 114: Line 220:
If you are still using the old assignment (2.2) module, after upgrading to Moodle 2.7 all assignment (2.2) activities will be hidden. You need to run the [[Assignment upgrade tool]] to un-hide the activities.
If you are still using the old assignment (2.2) module, after upgrading to Moodle 2.7 all assignment (2.2) activities will be hidden. You need to run the [[Assignment upgrade tool]] to un-hide the activities.


If you really, really need to keep using the old assignment (2.2) module, you should update the code to Moodle 2.7, and then replace the "mod/assignment" folder with the one from the plugins directory before completing the upgrade.
If you really, really need to keep using the old assignment (2.2) module, you should update the code to Moodle 2.7, and then replace the "mod/assignment" folder with the one from https://github.com/moodlehq/moodle-mod_assignment/releases before completing the upgrade.
 
===Maths filters===
 
Moodle 2.7 comes with a new maths filter based on [http://mathjax.org MathJax]. It is an alternative to the existing Tex filter. The MathJax filter is enabled by default for new sites and also  upgrades. You may wish to disable the Tex filter and enable the MathJax filter. In 2.7 sites, if both are enabled the TeX filter wins regardless of filter order because the TeX filter removes all TeX notation before the javascript is executed. This may mask the fact MathJaxloader is enabled on old installations.  In 2.8 both filters may be run together with both being used to display the mathematics. See MDL-44780. There are some compatibility settings and other options that can be changed for the [[MathJax filter]].


==Possible issues that may affect you in Moodle 2.7==
==Possible issues that may affect you in Moodle 2.7==


''Items to be added here...''
===Custom log-based reports===
 
Moodle 2.7 has moved to the new Logging API that allows more detailed and more flexible log storage. By default after the upgrade Moodle no longer stores data in table 'log'. All standard reports and plugins that used to access this table are converted to support both new API and legacy 'log' table. It is understandable that there might be custom 3rd party plugins that can not be changed immediately and either write significant information to the 'log' table or require access to it. In this case admin needs to enable writing to the legacy log:
Site Administration > Plugins > Logging > Legacy log : Select "Log legacy data". You might also want to disable "Standard log" so your system doesn't have double logging.
 
=== MySQL dmlwriteexception error when restoring a course===
 
If you obtain a  dmlwriteexception error when restoring a course, it is recommended that InnoDB tables are converted to the Barracuda file format. See the section 'Converting InnoDB tables to Barracuda' in [[Administration via command line]] for details of why this is recommended plus information on a tool for converting tables.
 
===MySQL dmlwriteexception error when using calculated questions in a quiz===
 
If you're using MySQL or SQL*Server and you have a problem with duplicated keys with the question_attempt_step_data table when using calculated questions in a quiz (from entering a formula which uses variables with the same characters in different cases), it is recommended that you upgrade to Moodle 3.0.x or higher ASAP. Alternatively, the problematic unique index can be dropped or the collation of the columns changed to be case-sensitive, however this is not considered a complete fix. See MDL-29332 for more information.


=== Moodle 2.3, 2.4, 2.5 and 2.6 improvements ===
=== Moodle 2.3, 2.4, 2.5 and 2.6 improvements ===
Line 131: Line 252:
==See also==
==See also==


* [[Installation]]
* Using Moodle [http://moodle.org/mod/forum/view.php?id=28 Installation problems forum]  
* Using Moodle [http://moodle.org/mod/forum/view.php?id=28 Installation problems forum]  
* [[dev:Moodle 2.7 release notes|Moodle 2.7 release notes]]
* [[dev:Moodle 2.7 release notes|Moodle 2.7 release notes]]

Latest revision as of 09:35, 22 September 2016

This page explains in detail how to upgrade Moodle. For a summary of the process, see Upgrade overview.

Check the requirements

Check that your server meets all requirements for 2.7 in Administration > Site administration > Server > Environment.

Note: You can only upgrade to Moodle 2.7 from Moodle 2.2 or later. If upgrading from earlier versions, you must upgrade to 2.2 as a first step.

Before upgrading

We advise that you test the upgrade first on a COPY of your production site, to make sure it works as you expect.

Themes

All standard themes present in Moodle 2.6 (and earlier), except the Clean theme, have been removed from Moodle 2.7 (see MDL-43784). Custom themes and themes from the Plugins Directory are not affected, unless they use one of the removed themes as a parent theme. If a theme that was in use has been removed, the theme will revert to the new default theme called Clean.

For sites wishing to continue using any of the removed standard themes (or themes relying on a standard theme as a parent theme), other than Clean, we recommend you use the following process.

  1. Download the 2.7 version of Moodle, but do not run the upgrade yet.
  2. Download the 2.7 version of your theme from the Themes section of the Moodle plugins directory (or from the links below) into moodle/theme/.
  3. Proceed with the upgrade.

It is possible to copy missing themes into Moodle after the upgrade, but this should happen before users touch the system, otherwise theme-related settings may be lost.

The affected themes (with download links) are...

Afterburner plugins db github
Anomaly plugins db github
Arialist plugins db github
Binarius plugins db github
Boxxie plugins db github
Brick plugins db github
Formal White plugins db github
Form Factor plugins db github
Fusion plugins db github
Leatherbound plugins db github
Magazine plugins db github
Nimble plugins db github
Nonzero plugins db github
Overlay plugins db github
Serenity plugins db github
Sky High plugins db github
Splash plugins db github
Standard plugins db github
Standard old plugins db github

Note: Only installed additional themes are updated automatically during the upgrade, NOT standard themes. Because standard themes have been removed from Moodle 2.7, they have to be re-added.

Questions engine upgrade

In Moodle 2.1, there was a major overhaul of the Question engine. As explained in the upgrade documentation for that version, it was possible to delay parts of the database upgrade to be run later. Before you upgrade to Moodle 2.7, this upgrade must be completed.

This will affect you if...

  • your site started off on a version of Moodle 2.0.x and
  • when you upgraded to Moodle 2.1 or 2.2, you made use of the complex facility to delay part of the question engine upgrade (as explained in the upgrade documentation for that version) and
  • you still have not completing that upgrade

...then you must complete it before upgrading to Moodle 2.7.

You can check by looking at the bottom of the Environment page in your site, providing you are running a version later than 2.4.9, 2.5.5 or 2.6.2. If you have a problem, it will tell you there. If there is no mention of questions there, you can forget about this.

This is unlikely to affect most users.

Backup important data

There are three areas that should be backed up before any upgrade:

  1. Moodle software (For example, everything in server/htdocs/moodle)
  2. Moodle uploaded files (For example, server/moodledata)
  3. Moodle database (For example, your Postgres or MySQL database dump)

See Site backup for more specific information.

Put your site into maintenance mode

Before you begin upgrading your site, you should put it into maintenance mode to stop any non-admin users from logging in.

Check for plugin updates

If you have Automatic updates deployment enabled, you will be able to update installed plugins automatically during the upgrade. Just make sure you check for available updates (via the button for it) at the Plugins check screen.

If you are updating plugins manually, it is a good moment now to check in the Moodle Plugins directory whether there is a 2.7 version available for any plugins (including themes) that you have previously installed on your site. If so, download the plugin package. In the next step, you will copy it to the appropriate location in your Moodle code (see Installing plugins).

The upgrade of the plugin will then happen as part of the Moodle upgrade process.

If an out-of-date plugin causes your upgrade to fail, you can usually delete the plugin code rather than uninstalling it from within Moodle so that the data associated with it is not deleted.

Install the new Moodle software

Standard install package

  1. Move your old Moodle software program files to another location. Do NOT copy new files over the old files.
  2. Unzip or unpack the upgrade file so that all the new Moodle software program files are in the location the old files used to be in on the server. Moodle will adjust SQL and moodledata if it needs to in the upgrade.
  3. Copy your old config.php file back to the new Moodle directory.
  4. As mentioned above, if you had installed any plugins on your site you should add them to the new code tree now. It is important to check that you get the correct version for your new version of Moodle. Be particularly careful that you do not overwrite any code in the new version of Moodle.
  5. Dont forget to also copy over your moodledata folder / directory. If you don't you will get a "fatal error $cfg- dataroot is not configured properly".

Linux

mv moodle moodle.backup
tar xvzf moodle-2.7.tgz

Next, copy across your config.php, any custom plugins, and your .htaccess file if you created one (check that custom plugins are the correct version for your new Moodle first):

cp moodle.backup/config.php moodle
cp -pr moodle.backup/theme/mytheme moodle/theme/mytheme
cp -pr moodle.backup/mod/mymod moodle/mod/mymod

Don't forget to make moodle/config.php (and the rest of the source code) readable by your www server. Ideally the files should not be writeable by your server.

If you use cron, take care that cron.php is executeable and uses the correct php command:

chmod 740 admin/cli/cron.php (some configurations need chmod 750 or chmod 755)
copy the first line from cron.php (if it looks like '#!/usr/local/bin/php' or '#!/usr/local/bin/php5.3', no need to copy '<?php')

if necessary.

Using Git

You can use Git for updating or upgrading your Moodle. See Git for Administrators for details.

Command line upgrade

On Linux servers, Moodle 2.7 supports running the upgrade from the command line, rather than through a web browser. This is likely to be more reliable, particularly for large sites.

Finishing the upgrade

The last step is to trigger the upgrade processes within Moodle.

To do this just go to Administration > Site administration > Notifications.

Moodle will automatically detect the new version and perform all the SQL database or file system upgrades that are necessary. If there is anything it can't do itself (very rare) then you will see messages telling you what you need to do.

Assuming all goes well (no error messages) then you can start using your new version of Moodle and enjoy the new features!

Note: If you are running multiple servers then you should purge all caches manually (via Administration > Site administration > Development > Purge all caches) after completing the upgrade on all servers.

Fatal error: Maximum execution time of 30 seconds exceeded...

If your server uses a main language other than English, you may encounter a 'Fatal error: Maximum execution time of 30 seconds exceeded' when you try to upgrade it. You can increase max_execution_time = 160 on php.ini to allow the scripts enough time to process the language update. Otherwise, you can switch to English as the default language before doing the upgrade and back to your original language after a succcessful upgrade. See the forum discussion at https://moodle.org/mod/forum/discuss.php?d=119598.

After upgrading

The config.php file from your installation should work fine but if you take a look at config-dist.php that came with Moodle 2.7 there are more/different options available (e.g. database drivers and settings). It's a good idea to map your old config.php settings to a new one based on the 2.7 config-dist.php.

Cron

Cron has received a major update (MDL-25499) and now has support for both scheduled and adhoc tasks.

The benefits of these changes are:

  • The schedule for every task can be configured by the admin
  • Tasks can run in parallel
  • Cron processes use locking to prevent the same task running at the same time by different processes
  • Clusters with multiple identical application nodes are supported, you can run cron on all of them

A result of this is that cron can be run much more often, which means (for example) forum posts can be sent out sooner. To take advantage of the new cron system it is now strongly recommended that administrators increase the frequency that cron is run to at least once per minute.

You also may need to modify any automated scripts you have that are parsing the output from cron. It is no longer possible to simply monitor the output of cron for the string "Cron script completed correctly" (if that is what you were doing). An alternative is to monitor the output for the string "task failed:". If you detect that a task is failing, here are some tips for debugging the failure.

Before the upgrade to 2.7, there may have been a cron task that was failing, which was preventing the rest of cron from being executed. A failure in any single task will no longer prevent the rest of the Moodle cron tasks from executing, so you may uncover previously masked bugs. It is a good idea to closely monitor the output from cron after the upgrade to 2.7.

Assignments

The old assignment (2.2) module has been removed from core and has been replaced by a stub to support transparently remapping URLs and restoring course backups from the old module to the new one.

If you are still using the old assignment (2.2) module, after upgrading to Moodle 2.7 all assignment (2.2) activities will be hidden. You need to run the Assignment upgrade tool to un-hide the activities.

If you really, really need to keep using the old assignment (2.2) module, you should update the code to Moodle 2.7, and then replace the "mod/assignment" folder with the one from https://github.com/moodlehq/moodle-mod_assignment/releases before completing the upgrade.

Maths filters

Moodle 2.7 comes with a new maths filter based on MathJax. It is an alternative to the existing Tex filter. The MathJax filter is enabled by default for new sites and also upgrades. You may wish to disable the Tex filter and enable the MathJax filter. In 2.7 sites, if both are enabled the TeX filter wins regardless of filter order because the TeX filter removes all TeX notation before the javascript is executed. This may mask the fact MathJaxloader is enabled on old installations. In 2.8 both filters may be run together with both being used to display the mathematics. See MDL-44780. There are some compatibility settings and other options that can be changed for the MathJax filter.

Possible issues that may affect you in Moodle 2.7

Custom log-based reports

Moodle 2.7 has moved to the new Logging API that allows more detailed and more flexible log storage. By default after the upgrade Moodle no longer stores data in table 'log'. All standard reports and plugins that used to access this table are converted to support both new API and legacy 'log' table. It is understandable that there might be custom 3rd party plugins that can not be changed immediately and either write significant information to the 'log' table or require access to it. In this case admin needs to enable writing to the legacy log: Site Administration > Plugins > Logging > Legacy log : Select "Log legacy data". You might also want to disable "Standard log" so your system doesn't have double logging.

MySQL dmlwriteexception error when restoring a course

If you obtain a dmlwriteexception error when restoring a course, it is recommended that InnoDB tables are converted to the Barracuda file format. See the section 'Converting InnoDB tables to Barracuda' in Administration via command line for details of why this is recommended plus information on a tool for converting tables.

MySQL dmlwriteexception error when using calculated questions in a quiz

If you're using MySQL or SQL*Server and you have a problem with duplicated keys with the question_attempt_step_data table when using calculated questions in a quiz (from entering a formula which uses variables with the same characters in different cases), it is recommended that you upgrade to Moodle 3.0.x or higher ASAP. Alternatively, the problematic unique index can be dropped or the collation of the columns changed to be case-sensitive, however this is not considered a complete fix. See MDL-29332 for more information.

Moodle 2.3, 2.4, 2.5 and 2.6 improvements

Depending on which version you are upgrading from, please see the section 'Possible issues that may affect you' in the documentation

See also