1. In 2006, I completely converted one of my larger forum's sql tables collation to "utf8_general_ci" (UTF-8 Unicode) and never ran in to any problems - not even password problems.
I can imagine password problems would be the worst case scenario, with users unable to log in.
Just a few questions if I may about how this worked out in your case:
1. How large was your forum at the time of the conversion (let's say GB-wise for a MySQL dump to get a general picture)?
2. How did you go about doing the conversion - what exact script/command line/etc. did you use for your particular charset conversion?
3. How did you run the actual conversion? Was it via something like PHPMyAdmin or did it run as just a SQL database query?
4. Did the entire conversion script/process take a long time to run?
For the web page display, you can easily do the "modification 2" which I also mentioned aboveupdate in the language files / header meta tags from "iso-8859-1" to "utf-8" @ Control Panel > Languages > Language Editor > generic.php > CHARSET
This has no affect on the database and anyone can do this. It just simply tells browser/crawler what character set to expect/display the page as, rather than leave decision up to the browser/crawler to determine.
As for the questions you're asking now, regarding the database;
1. mine is roughly 800MB as a complete mysqldump FORUM.sql file.CLOSE YOUR BOARD BEFORE YOU START WORKING ON IT!!!
a) I used putty to ssh in to my server and used the following format to backup my DB:
mysqldump -username -password ubbt_forums > ubbt.sql
DETAILS @ https://www.ubbcentral.com/forums/ubbthreads.php/topics/191156#Post191156
b) I then made a duplicate of the database on my server, using MySQL
i) select the database
ii) go to its "Operations" tab at the top
iii) in the "Copy database to:" field, tape the name of your backup database, such as "ubbt-BAK" - be sure that "Structure and data", "CREATE DATABASE before copying" and "Add AUTO_INCREMENT value" are all checked ON -- others in that category are checked OFF. Click "Go" when ready.
NOTE: if anything goes wrong for you, just delete your current database and rename your backup what your working database was named, ie; remove the "-BAK" from its name.
2 & 3. prepare for "i got my backups. no need to cross fingers. lets just get this done" mode:
After you've confirmed that you have backups and that everything looks right, go back to the "ubbt" database's "Operations" menu (you're probably still there)
i) In the "Collation:" group, choose "utf8_general_ci" from the drop-down menu. Click "Go".
ii) from the left table listing/column, go in to the first table of your database, "ubbt_ADDRESS_BOOK" for example.
iii) click "Operations" from the top tab group
iv) in the "Table options" group, choose "utf8_general_ci" Collation. do not change any other options. Click "Go". Repeat this step for the other 64 tables in your "ubbt" database.
4. See item "iv" above
It took me about 10 minutes to totally complete that step for my entire ubbt database.
REPAIR your tables (also through MySQL) so your tables are optimized as they are rebuilt (this is also what what the sql REPAIR command does).
i) Select the database name from the top ("ubbt")
ii) When all the tables are listed, click on "Check All" on the bottom left. Choose "Repair table" from the drop-down list.
Next, inside your UBB.Threads control panel, rebuild your tables.
i) in Control Panel > Content Rebuilder. Rebuild posts, Topics, Forums, Signatures, and Private Messages.
This last step is probably overkill, but i did it without loosing any sleep worrying about not doing it.
Finally, login and visit a few forums and their posts to test if everything is as you expect it to be.
If things go smoothly, no one will notice anything. If there are hiccups, you have a backup to revert to.
One side effect that you/your members MIGHT come across, is some single byte characters (such as Swedish Ã¥, Ã¤, Ã¶, the temperature degree symbol, 1st/2nd/3rd...etc symbols, and most notoriously, Microsoft Word's backwards-single-quote " ' ", to name a few) will look like a black-box-single-character. This has no effect on your forum's function. It's only a display issue that you may run across once in a blue moon. If it bothers you, edit the post to replace the black-box-single-character with its equivalent character (ie; replace a backwards-single-quote with a standard single-quote)
If you read this post and don't understand what I've written, do NOT perform the update to your site. Have a professional take care of that task for you.
Take what I've written only as a "quick & dirty summery" of the steps one can take to accomplish this desired task, not as an absolute guideline.
Again, if you read this post and don't understand what I've written, do NOT perform the update to your site. Have a professional take care of that task for you.