I begun working for a company 2 months ago. It's my first job in a big enterprise. The problem is that in a lot of days I've nothing to do except having to read internal docs. And the main part of the coding tasks are modifying very small part of the already existing huge code-base, not rarely a single char in a line. Sometime I fell like I'm not good, because I can't find what it can be the required solution. I can do my solution of course, but it's not what they require. I had little or no support from senior members most of the time. I feel like I'm steeling my salary but... It isn't even high (19k per year in south EU). I think that I'm going to change my job, or at least my company. Hopefully before that they make the choice for me because I'm not adapting. But... What do you think? It's normal or I'm unlucky? Before this job I worked in small enterprises, and it was very different (always a lot of job, even too much, and a lot of freedom and "just it works" philosofy)
This is how big enterprise works. In so many cases, a person is hired and then the manager learns that there is a new person on the team. The manager doesn't have tasks ready for a new person. It takes a while for the organization to find the right work for this new person.
Some stories: A large Aerospace company in CA was known for hiring people and putting them in a trailer for 6-9 months while the security clearances came through. That gave the managers time to find what that new person could be assigned to.
A relative (with PhD and decades of experience) went to work for Chase in NYC. He endured weeks of reading corporate documents before getting to work on the stuff that they said they hired him for.
In short, this behavior is totally normal for huge corporations. It will change.
You might just be experiencing Imposter Syndrome. If you have 1-on-1 meetings with your boss, then that would be a good time to ask for feedback, be it positive or negative. If you don't have 1-on-1s, suggest it to your boss. You could also ask your boss for a mentor that could help you every so often.
Whenever you are left with nothing to do, ask your boss for tasks, and what to do when you run out of tasks (as @JoeStrazzere pointed out). Otherwise, do things to improve yourself (e.g. learning new technologies, reading industry articles) or to improve certain processes at the company.
I have been worked in a big company for many years, I can tell you, there is nothing strange in your case, big company more or less the same.
You would have your "formal" work to do after few months or even after probation. Similar case is very common.
Don't think about your salary, until your whole family rely on your salary. What you need to do is learning, learning your professional knowledge. Being working record in big company would great great help your career!
When I began my new job two years ago, I spend the better part of two weeks reading and cleaning out old files before I was trained to do what I do now. My boss warned me, "be thankful for the occasional downtime...it doesn't happen all that often."
There are times where it does feel chaotic, but I do appreciate those times when I have a free moment or two to relax, take a breather, and then focus on what needs to be done.