The Xindi database stolen by Enterprise NX-01, at the outset of the starship's voyage in the Delphic Expanse, was one of several key intelligence prizes snatched by Starfleet during the search for the Xindi weapon. It contained comprehensive data about the Xindi, who were largely ciphers to both Starfleet and the Vulcan High Command at the time. Knowledge gained from the database heavily influenced Jonathan Archer's response to the Xindi threat.
Circumstances of retrievalEdit
The database was obtained by an Osaarian merchant ship from a Xindi spaceship which they attacked. After the Enterprise encountered the pirates' hideout in a mysterious and ancient sphere, Ensign Hoshi Sato surmised that such a database was also in the pirates' possession, and would aid the Enterprise's search for the Xindi.
With the access codes having been acquired from an Osaarian pirate that Captain Archer was holding in the brig, the database was forcibly downloaded via a com-link by Sato, as Enterprise flew less than a kilometer away from the pirate ship. (ENT: "Anomaly")
Archer not only attempted to use this database in order to locate the Xindi weapon but also operated it to learn much about the Xindi themselves, including the different species of which that group was comprised. (ENT: "Anomaly")
For instance, it was through this database that he first became aware of the Xindi-Arboreals, knowledge that later allowed him to make a positive identification of such individuals when he actually encountered them for the first time. (ENT: "Extinction", "The Shipment")
Possible loss Edit
After helping a religious order which had run into trouble, Enterprise was commandeered by the group's leader, Pri'Nam D'Jamat, who determined that Archer had desecrated the spheres, which were central to D'Jamat's religion. As punishment, the Pri'Nam deleted a significant portion of the Enterprise database, though it wasn't clear exactly how much of the Xindi database was affected by this purge. (ENT: "Chosen Realm")
Diminished importance Edit
This more specific information – along with the fact that Archer tricked Degra into revealing the location of the weapon – presumably superseded the information in the database. (ENT: "Proving Ground", "Stratagem", et al.)