Thanks for the update.

Arrays...

Textfiles...
Look into the manual for the 'file_load', 'file_save' and 'add_buffer' commands.
They will let you load the whole textfile into memory, and read/write to it as per normal,
WITHOUT actually accessing the hard-drive. Then save any changes if you WANT to.

Structs...
Keep practicing. Its worth the effort. (even though you'll NEVER actually STOP practicing).

SQL/GSTlite...
I expected it would be.... BUT see my next point.

AFAIK WOW uses a SQL look-alike if not actual Microsoft SQL-server itself.
I know that if you download one of the "private server" packages for WOW,
they have a little server app that hovers over the free "MySql" database.
You then connect to it using the standard WOW client software.
This suggests to me that Blizzard(ie WOW) have multiple dedicated SQL servers,
linked up to replicate data to each other, each with its own "WOW server app" floating on top.