Prerequisites for MySQL

Applicable for Engagement Services

Create the database needed for Engagement Services with unicode character set as UTF8. Also ensure that you modify the my.cnf or my.ini with the following parameters:
[client]

default-character-set = utf8

[mysql]

default-character-set = utf8

[mysqld]|

character-set-client-handshake = FALSE

collation_server='utf8_unicode_ci'

character_set_server='utf8'
Next, restart the MySQL service and run the following query to verify the details:
mysql> show variables like '%coll%';
+----------------------+-----------------+
| Variable_name | Value |
+----------------------+-----------------+
| collation_connection | utf8_unicode_ci |
| collation_database | utf8_unicode_ci |
| collation_server | utf8_unicode_ci |
+----------------------+-----------------+
3 rows in set (0.00 sec)
mysql> show variables like '%char%';
+--------------------------+----------------------------+
| Variable_name | Value |
+--------------------------+----------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | utf8 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | utf8 |
| character_set_system | utf8 |
| character_sets_dir | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+

Applicable for Identity Services

If you are using any lower versions of MySQL 5.7 such as v5.7.12 or lower during installation, you may encounter an error due to which the installation rolls back. This error occurs due to a bug in the MySQL database. For more information, refer to MySQL Bugs

The error details are as follows:

Error: Migration V810_27_01__DeleteDuplicateAcsUserIdProviderGuidRowsAddUniqueConstraint.sql failed
SQL State: HY000
Error Code: 1093
Error Message: You can't specify target table 'users' for update in FROM clause
Location: <Location where the installation is done>

To resolve the error, follow these steps:

Execute the following command before running the installer:
```
SET GLOBAL optimizer_switch = 'derived_merge=off';
```
Once the installation is done, set derived_merge ON using the following command:
```
SET GLOBAL optimizer_switch = 'derived_merge=on';
```

Steps before installing (or) upgrading Fabric with an existing database

Perform the following activities before installing (or) upgrading Quantum Fabric with the existing database:

Take a backup of your database.
Make sure you have a previously installed directory.
Take a backup of the applications that are deployed at the server level. After the installation is complete, take a backup of the changes that were made to the binaries.
After the installation or upgrade process is complete, replace the old authService.key, workspaceService.key, and ACCOUNTS_ENCRYPTION_KEY keys.
This is only applicable for the identity and workspace components.

Create /tmp Folder

Quantum Fabric Installer requires a /tmp folder in a Linux environment to unpack the installer. When the /tmp folder is not found, the Installer displays an I/O exception at the time of unpack exception.

This must be specified in the pre-req of installation. Installation requires temp folder to unpack MF installer (either default / custom temp folder).