Release databases are maintained to provide release groups with a service for checking existing release titles (i.e., to avoid duping another group). Some databases contain historical release records dating back to the BBS era. Note that such databases are uncommon, due to a completely different release naming method (based on the ZIP file descriptor FILE_ID.DIZ, as opposed to a directory name), and lack of information from this period. Release databases are usually updated by automatic processes that either recurse selected topsites searching for new releases (spidering), or catch pre-release announcements from site channels. Release databases used by topsites are private, but a number of public websites exist with similar information. Credit system Credit system controls the amount of data that users can download. Most sites operate by using an automated credit system. When a user uploads a file, their account is credited for an amount based on the uploaded file size, commonly multiplied three times. For example, when a user uploads a 15MB file, they may receive 45MB credits in return. Credits can be later used to download files from the site. Credits can be lost by uploading a bad release that gets nuked. Nuke multiplier affects the amount of lost credits. Nukes can be either site nukes (local) or scene nukes (global). Site nukes are issued when a release that is uploaded to the topsite violates site rules, such as 'No VLS' for the MP3 section. Another common site nuke is for backfilling, which is uploading something after a specific amount of time has elapsed from the time of release, usually 5 to 15 minutes. Typically the nuke multiplier for a site nuke is at least 3x, where all couriers responsible for racing the bad release will lose 3x the credits they gained uploading. These nukes will not be echoed out to pre channels, as they only affect the local site. Scene nukes are nukes which are echoed out to pre channels. Scene nukes usually occur when a release violates scene rules, such as wrong encoder, or when the release is outright bad, such as out of sync. The nuke multiplier for scene nuke on topsites is usually 1x; all the couriers lose all credits gained uploading the release and break even. Affiliates A warez group may gain access to a topsite as an affiliate (or "affil"), thus making the site among the group's primary distribution points. Affiliation benefits