There are too mant TREX Errors

Hello Experts,

I have created an Index for a specific folder in KM.

Under KM--> Sys Conf --> KM --> Index Administration it shows the green led, which I believe that the data sources are completely indexed. But, under the KM--> Monitoring > KM> Indexing Monitor , it says:

Status = red led (There are too many TREX errors)

Status = Active

In Process = 142678

Indexed = 51345

Errors = 10849

And, when I opened the list of errors there are many Crawler and Trex: Preparation failed: index operation

Can you suggest, what's the mistake that I am doing or do I have to any additional configurations for the index that I have created??

Thanks,

Raghava