HD Witness v2.1 had different index file type than Nx Witness v2.3 and later - when the Server Hive Architecture was introduced. Originally the file was a .csv table. The limitations for this file really were disk space. Also, the file size would never really increase over time.
Now, with the SQlite introduced when Nx Witness starts to overwrite recordings it also starts edits the db file removing the oldest lines.
Typically the db file size tops out at around 300 Mbytes for ~10 TB of archives.
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