!!! Overview
[{$pagename}] ([VLR]) is a [database] of the subscribers who have roamed into the [jurisdiction] of the [MSC] ([Mobile Switching Center]) which it serves. 

Each main base station in the network is served by exactly one [VLR] (one BTS may be served by many [MSCs] in case of [MSC] in pool), hence a subscriber cannot be present in more than one [{$pagename}] at a time.

The [data] stored in the [{$pagename}] has either been received from the [Home Location Register], or collected from the [Mobile Station]. In practice, for performance reasons, most vendors integrate the [{$pagename}] directly to the [V-MSC] and, where this is not done, the [{$pagename}] is very tightly linked with the [Mobile Switching Center] via a proprietary interface. Whenever an [Mobile Switching Center] detects a new [Mobile Station] in its network, in addition to creating a new record in the [{$pagename}], it also updates the [Home Location Register] of the mobile subscriber, apprising it of the new location of that [Mobile Station]. If [{$pagename}] data is corrupted it can lead to serious issues with text messaging and call services.

Data stored include:
* [IMSI] (the subscriber's identity number).
* [Authentication] data.
* [MSISDN] (the subscriber's phone number).
* [GSM] services that the subscriber is allowed to access.
* access point ([GPRS]) subscribed.
* [Home Location Register] address of the subscriber.
* [SCP] Address(For Prepaid Subscriber).

!! More Information
There might be more information for this subject on one of the following:
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