I am always surprised as to how often I find people who feel that the only way they have job security is if they are the only ones that can do their job.
Nothing could be further from the truth. If you are the only person that can do a particular job for your company then you are putting yourself more at risk for losing that job than you may realize. What you see as ‘security’ your management may see as ‘risk’. They could easily decide to outsource your function or role in order to reduce that risk.
Now consider the person who looks to perform their tasks and share knowledge with others. They are not afraid to document how things are done, so that others can understand how things work. They are able to take a vacation day without having to answer the phone or email to help solve a problem because others on the team would already know what to do in their absence.
If your whole strategy to job security is to funnel everything through you, that you want to be a silo of knowledge, then you are going to be seen as a bottleneck at some point.
And we all know that when it comes to increasing performance, we look to remove bottlenecks.