I have created an account and setup a domain. When I tried the whois lookup the domain is referred to as available for registration. But when I take the Domains tab, it is showing a registrar error as follows :
An unknown fault occurred-please contact support
If the whois data is for a thick registry like .org, the data is updated in real time when the registrar gives it to the registry. And if the registry is under heavy load, whois queries take a back seat to registry operations.
If you're talking about a thin registry like .com, the whois data is managed by the registrar, not the registry. If a domain gets registered, but the registrar's whois hasn't updated, the registrar's whois server might report the domain as being available when it's not.
So any delay in updating the whois, whether on the part of the registry or the registrar can yield a misleading result. The only authoritative result is a direct check of the registry for a domain's availability.
^ My thoughts exactly. You should not rely on 'services' like DomainTools to check the availability of a domain, but rather perform a real-time whois search at the Registry directly. The easiest and most convenient way for this is a plain old whois command in your command prompt.
^ But because whois data can lag, I prefer to do an actual domain check. Besides, if I'm checking availability, I'm registering it. But, yeah, if one insists on using whois, query the registry directly, and don't waste your time with a registrar's or other third-party's web-based whois.