The Archives Mother of the Bene Gesserit first, then later, the combined Gesserit/Honored Matres group, the New Sisterhood; was in charge of the complete maintaining of all records pertaining to human-kind for both organizations. The information was kept in its' entirety at the Chapterhouse Keep.
The role was especially important during the time of the advent of Kralizec, as the current Archives Mother, Accadia, was in charge of gathering all information that Sisters and Reverend Mothers who had survived the initial onslught of the rampaging Honored Matres into humanity. For example, she had the survivors of the pillage of Lampadas, the library world, share their information with other sisters. Then each recorded the massive quantities of data onto shigawire spools to create a permanent record.
When the groups combined a few years later, Accadia, as Archives Mother, had the latest generation of Honored Matres share their stories for cataloging and correlation. The assimilated Matres knew they were fleeing from a great Outside Enemy, but they could not remember in their own historical records who this Enemy was. What was known was that countless Scattering-Matres planets had been wiped out in entirety of all populations by a deadly plague.
But over the course of three decades of gathering and correlating such data, and the addition of Murbella's own knowledge of Lenise bounding onto the reborn Thinking Machine Empire, Accadia was able to ascertain the Thinking Machine Enemy's path towards the center of human-kind.
At a great convocation on Chapterhouse after the destruction of the last rebel Matre group on Tleilax, Murbella had Accadia present to all convened, the path of first the Matres into the Old Empire; then the path of the deadly plague, the Omnius Scourge into Scattering worlds. Accadia came to the conclusion as most of those gathered, the Thinking Machines were headed for the heart of human-kind, Junction and Chapterhouse.