vBulletin code question

[sturdevk]

I have a technical question:

how the vBulletin app prevents the overwriting records in the datastore table?

for example, two admins are both adding new forums at the same time, as I know, it involves to read forumcache string from datastore table;unserialize it to php object; update this php object; serialize this object back to forumcache string and update datastore table with new forumcache string.

During this process, what if one process read out the forumcache string from DB, another process also read out this string from DB before the first process update this string in DB, in this case, second process will overwrite the first process's update on forumcache string, is it?

if vBulletin code will prevent this case from happening, could anybody point out which part of code doing this prevention?

Thanks,
a PHP newib who starting php programming 1.5 month ago