Let this be recorded

Let this be recorded for a generation to come, so that a people yet to be created may praise the Lord (Ps 102:18).

This verse lays down a fundamental principle. As one scholar notes:

That God saved his people from exile needs to be written down to ensure that future generations will know of his saving acts and proclaim his name. 

Let…be written is to ensure its accuracy and permanence. This is for the benefit of the following generation. B. Waltke et al., The Psalms as Christian Lament (Eerdmans 2014), 232.

That's a sola Scriptura principle. To an ensure the accurate transmission God's words and deeds for the benefit of posterity, there needs to be a written record.

i) We remember events better than words. We remember the gist of what somebody said.

ii) Oral tradition is an inefficient means of mass communication. Word-of-mouth is provincial. Writing is a more efficient means of disseminating information in space and time.

iii) In oral tradition, moreover, you keep adding links to the chain of custody. Every time it's repeated (or paraphrased), that's one more step removed from the source.

As another scholar notes: 

Ezra-Nehemiah are a fulfillment of this declaration; they put into writing the story of the city's restoration. J. Goldingay, Psalms: 90-150 (Baker 2008), 157.

To verify prophetic fulfillment, it's useful to have a written record of the oracle in advance of the fact. That establishes the priority of the oracle, as well as the wording. And that's something which posterity can consult after the fact. 

Lay Catholic apologists are fond of quoting 2 Thes 2:15 to prooftext their appeal to oral tradition. But that's anachronistic. 

If I were a mid-1C Christian in a church which Paul planted, if I heard him preach, then I'd hold fast to what he taught me in person. That's very different from what Catholicism means by oral tradition.