update sql patch instructions. fixes #5630

Author: jnorell

install/sql/README.txt

@@ -9,18 +9,24 @@ then follow these steps:
 1) Add the field or table in the ispconfig3.sql file. This file contains the
    complete database dump which is used when ISPConfig gets installed.
 
-2) Create a new file in the "incremental" subfolder wich contains the alter 
-   table, or if it is a complete new table then the add table, statement(s) in 
-   MySQL syntax which is/are required to modify the current ispconfig database 
-   during update. The naming scheme of the sql patch update files is 
-   upd_0001.sql, upd_0002.sql, upd_0003.sql etc. Ensure that the number that 
-   you choose for the new file is a +1 increment of the number of the last
-   existing file and that the number is formatted with 4 digits.
+2) Edit the file "incremental/upd_dev_collection.sql" which contains the SQL
+   statements (alter table, add table, update, etc.) in MySQL syntax which
+   are required to modify the current ispconfig database during update.
+
+   The upd_dev_collection.sql file contains all db schema modifications
+   for changes made since the last ISPConfig release.  If SQL statements
+   are already present in the file when you make your additions, add yours
+   to the end of the file, and do not remove any existing statements.
+
+   When a new ISPConfig update is released, the contents of
+   upd_dev_collections.sql will move to an sql patch file, using the naming
+   scheme upd_0001.sql, upd_0002.sql, upd_0003.sql etc.
 
-   A patch file may contain one or more alter table statements. Every patch file
-   gets executed once in the database, so do not modify older (already released) 
+   A patch file may contain one or more SQL modification statements. Every patch
+   file gets executed once in the database, so do not modify older (already released)
    patch files, they will not get executed again if the update was already run 
-   once on a system.
+   once on a system, and will result in missing updates on any system where they
+   have not run yet.
 
    After a patch has been executed, the dbversion field in the server table gets
    increeased to the version number of the last installed patch.