For transporter systems, pattern buffers were also synonymously referred to as a transporter buffer, transporter pattern buffer, transport pattern buffer, or simply transport buffer.
The buffer was used during matter-energy conversion to temporarily store the matter stream following dematerialization, but prior to sending the stream to its target. This was done because of the relative motion of transporter and target. By temporarily storing the matter stream, the Doppler compensators had enough time to adjust the targeting scanners.
The buffer capacity could be expanded, "in a pinch", to transport several dozen occupants at a time. This was not usually a preferred method of operation on account of safety reasons. (VOY: "Prophecy")
The transporter buffer performs it's own version of a microcellular scan every time someone uses it. In reviewing transporter logs, it was possible to observe the first time an anomalous reading might have appeared in an individuals molecular pattern. (VOY: "Favorite Son")
A matter stream could not be stored indefinitely in the buffer. The only known occurrence of a person surviving in a buffer longer than the theoretical maximum was Captain Montgomery Scott on board the USS Jenolan. Following the Jenolan's crash landing on a Dyson sphere, Scott, with the help of Matt Franklin, was able to store his pattern in the buffer for 75 years. This was achieved by disabling the rematerialization subroutine, connecting the phase inducers to the emitter array, bypassing the override, and locking the buffer into a continuous diagnostic cycle. Although Captain Scott's pattern suffered less than 0.003% degradation, and was successfully recovered by Geordi La Forge of the USS Enterprise-D in 2369, Franklin was irretrievable, as one of the inducers had failed, causing a 53% degradation in his pattern. (TNG: "Relics")
In 2152, diamagnetic storms saturated with polaric energy were encountered on a planet visited by the crew of the starship Enterprise. The storms interfered with the operation of the ship's transporter, resulting in Hoshi Sato being trapped in its pattern buffer for 8.3 seconds while Malcolm Reed worked to reintegrate the matter stream. (ENT: "Vanishing Point")
A pattern buffer malfunctioning was the leading cause of transporter accidents. In the 2270s, during the V'ger incident, Commander Will Decker and Lieutenant Cleary did repairs on the pattern buffer but it malfunctioned while Cleary was replacing the transporter sensor. Janice Rand attempted to beam Commander Sonak and a female officer aboard the Enterprise but they were both killed. Scotty later repaired the pattern buffer and the sensor in time to beam Ilia and Leonard McCoy aboard. (Star Trek: The Motion Picture)
In 2367, when Lwaxana Troi became agitated upon not being allowed to transport to Kaelon II and her daughter tried to talk her down, Miles O'Brien stated that he would go check the pattern buffers and left to give the two privacy. (TNG: "Half a Life")
When weapons were beamed to a rebel camp on Krios from a cargo transporter of the Enterprise-D that same year, Miles O'Brien asked Geordi La Forge if he could check the reliability of the pattern buffers. (TNG: "The Mind's Eye")
In 2372, Odo began to experience the effects of an unknown affliction that he had acquired from his fellow Changelings, which caused the destabilization of his molecular structure. When it was proposed that he be ferried aboard the USS Defiant to the Founders' new homeworld, the crew had to wait for Odo to carry himself aboard the ship. When it was questioned why he couldn't go through the transporter, Doctor Julian Bashir explained that "his molecular structure is scrambled enough as it is," adding, "[t]he last thing he needs is a trip through a transporter buffer." (DS9: "Broken Link")
When the Orion Syndicate planted a bomb on board the USS Rio Grande, Odo was able to mitigate the damage from the bomb by beaming it out and channeling the explosion through the transporter buffer. (DS9: "The Ascent")
Pattern buffers were also a component used in holodecks, and were also synonymously referred to as the holodeck buffer, holo-buffer or even just straightforward "the holodeck's pattern buffer." (VOY: "Latent Image", "Inside Man", "Renaissance Man")