An SH Server (SHサーバー, esu icchi saabaa?) is the computing device that contains and processes the Static H-Waves of the Reyvateils, or in other words, their Cosmospheres. As it might be easy guess, SH Server is simply the abbreviated form of Static Hymmno-Server.
These devices are the main parts of the Song Servers, and the lifelines for all of the Pureblooded Reyvateils. Actually speaking, one of the main parts of the Soulspace of the Reyvateils, the Spiritual Standard Frequency, contains the parameters that indicate to which SH Server said Reyvateil is connected, together with their access authorizations and other system-related things.
If these Servers were shut down or destroyed, or if the Reyvateils went beyond the reach of the SH Server's influence, the Reyvateils to which they are connected would lose the connection to their Cosmospheres, causing different effects depending on if they are Purebloods or Halfbloods.
If they are Purebloods, the Triangular Nuclear Loop located within them will stop functioning, with the consequence that their bodies won't be able to continue existing, and revert into biofluid, killing them off.
As for the Halfbloods, this wouldn't kill them because they have still their Soulspaces stored within their brains (the one in the SH Server is a mere replica). However, they would lose their Reyvateil qualities and would have to remain as normal humans.
There are a two main kinds of SH Servers: the Origin Exclusive Servers, and the β-6D Servers.
Origin Exclusive Server
This type of SH Server is made exclusively to hold the Binary Field and Soulspace of a Reyvateil Origin. Unlike the β-6D Servers, they lack the partitioning function, so they aren't capable of containing multiple Soulspaces at once. However, this is made up by the fact that these Servers have specialized functions that can't be replicated in any others, such as Shurelia's hard wiring, which allows her to fully control Ar tonelico, or the sampling and recording of extremely high frequencies unique to Tyria's server.
As an extra note, Tyria's SH Server does support partitioning due to the Archia Think Tank inserting an special SH-RAM area in it, with allows it to emulate the capabilities of the β-6D Servers. However, this was made just as preparations to create the only γ Sublimated Reyvateil in existence, and it's unknown what would happen if any other Reyvateil was allocated inside it, since Sakia's Cosmosphere itself occupies the same space that tens of Pureblooded β-types would occupy in β-6D.
Known Origin Exclusive Servers
This is an SH Server containing the consciousness of a single incorporeal Reyvateil, called β-6D. However, this large Soulspace is fragmented into more smaller compartments, which are used to contain the Cosmospheres of all the Pureblooded β-type and Third Generation Reyvateils. However, it does have the disadvantage of having the same wave frequency limit as a human mind: 10^11 Hz. Due to this, more specialized Reyvateils can't be linked to them, and need to have their own dedicated SH Servers.
In addition, while the only β-6D Servers currently in existence (Ar tonelico β-6D and Harvestasha β-6D) are very similar, they aren't compatible with each other due to programming differences. In other words, this is due to the support for EXEC_FLIP/. programs that is exclusive to the Harvestasha β-6D.