Dear Edwin,

It is possible to propagate the sql udpdates to the slave sites?

I have updated my component in the master site and the :master_db: has been updated correctly, but not the slave sites db. In the update, there is an "ALTER TABLE" which adds a new column to the db.

How does it work?

Thanks for your help!

2 possibilities to do that.
1) Go in the back-end of each slave site and perform the "Extension Maanger" / Database => and click Fix button

2) Use the JMS "maintenance" menu that is able to scan all the websites and compare the current DB structure with different sources
either :
- "THIS" websites (normally the master)
- When JMS has a settings that make the "multisites" pointing outside of this website, you can also have "master"
- It is also able to retreive the "update" files from the core of joomla
- Also search for the full installation of joomla but also the extension

The complexity with the "maintenance" menu is to select the correct source of SQL that you want to use as reference.
When you have selected to correct source, the maintenance menu provide you a "check DB" to compare the DB structure according this source.

The "maintenance" is able to parse and interpret (analyze) more SQL statement than the Joomla Database fix.
In addition the "maintenance" / "check DB" provide more information than the "Extensino Manager / Database :
- OK
- has error
- or didn't understood the sql (Skipped)

In addition, it also check the extension DB structure (not only the Joomla Core)

Once you have identified the correct source that you want to apply, you can perform the "Fix" or "Fix with skipped".

You can also decide to execute some "free sql".

There are also more complex functionalities that is designed to create a kind of "legacy mode".
The legacy mode has for objective to allow several joomla version runing on the same DB (website).
The objective is to be able keep old joomla version extension with new joomla.

This explain why JMS has setting to connect on a "remote" multisites.
So that you can have several master with different joomla version and share the same JMS websites definitions.
As you can put in JMS slave site with domain that contain a kind of subdirectory (SEF like), you can decide to have some SEF menu that are runing under different Joomla version and sharing the same DB content.

As you can see, this open a lot of possibilities. But this is complex.

When performing massive DB modification, it is strongly recommended that you perform a backup.