In this continuity, the Sivas were a sub-class of the Syracuse-class destroyers.
USS Siva (NCC-520) was a Syracuse-class destroyer—lead ship of the Siva destroyer subclass—in Star Fleet service during the the mid- to late-23rd century. The newbuild members of the subclass were intended to enhance the fleet's escort capacity through the adoption of the radically new dilithium-regulated propulsion systems and the PB-31 nacelle with its FWD-1 (and later FWD-1A) coils. The changes to support the new power generator required a profile change from the Syracuse-style saucer. In order to accommodate the operational, tactical, and support equipment the ship needed for its continuing anti-capital/anti-installation role, the saucer had to be modernized.
In 2250, Siva was the first of the Sivas and the remaining Syracuse vessels, as well as eight Monoceros from the Hermes-class scouts, to undergo upgrades of the external hull, warp nacelle, pylon, and weaponry. The new PB-32 nacelle provided cruise and maximum speeds of warp 6 and warp 8, while the weaponry was completely replaced: the torpedo systems were modified to support forced-intermix warhead supply equipment and the six phase cannons were replaced by an equal number of less massive—but far more adaptive—Type VII phaser emitters. The bridge was provided a lower target profile by being “sunk” half a deck into the surrounding superstructure. And, for utilitarian purposes, a powerful tractor beam emitter was mounted on the pylon’s trailing edge, midway between the saucer and the nacelle.
Siva was laid up for most of 2274 and 2275 for engineering testing for class modernization eith yet another attempt to improve on the destroyers' maneuverability at warp. An inverted LN-64 provided the new linear technology and, once integrated and tested, the ship received another, similarly placed on the dorsal. Unfortunately, even with the advanced nacelle, the improvement did not exceed that of the Pompey subclass of a decade earlier.
Despite the lack of a revolutionary improvement, Siva was still more capable than when in her previous Flight II configuration and Star Fleet decided to retain her as a fleet escort. Tthe removal of the two (now) light torpedo tubes from her dorsal saucer was authorized and a single heavy torpedo launcher was added low on her ventral pylon. The ventrally-mounted dish had to be removed and some old, familiar equipment of the long-ago Syracuse/Saladin days was broken out of storage: the deflector emitters were installed at similar locations on Siva.
USS Siva remained operational in her lone Flight III configuration, including as a reserve and then training vessel, until 2301. (Delta Dynamics: Star Fleet Starship Recognition Manual: Report #292: Syracuse Destroyers)
In this continuity, the ship was named Shiva, and was referred to as a "second-generation Class I destroyer". (Starship Dynamics: General Plans U.S.S. Shiva NCC-520 Mk-VIII-A Destroyer Shiva Class)