Question to pjiang Re:A# 确定下来之后，接下来就看最近一年之内有没有申请过签证

In your blog, you memtioned
A# 确定下来之后，接下来就看你最近一年之内有没有申请过签证。如果是，那你的 G-325A 表中蓝颜色的那份，就被送去你当初申请签证的领馆。大家还记得，老师曾经提到过的 G-325A 彩色打印吧，虽然不是必须的。因为 DOS 只保留最近一年的签证记录，入境超过一年的同学，就略去了这一步。

what DOS stands for here? Department of States?
Just don't understand if "G-325A 表中蓝颜色的那份，就被送去你当初申请签证的领馆" then why "因为 DOS 只保留最近一年的签证记录"
I thought DOS and consulate are two diffrent places/dept

Also, DOS 只保留最近一年的签证记录, what about the consulate overseas? how long they will keep visa applicants info?

Thanks