Can someone please explain to me how President Obama "opened our borders"?

I was having a discussion on Facebook in the middle of which I said that I was more or less satisfied with Obama's presidency. Then another guy I knew joined the conversation saying that Obama was a failure because he "opened our borders", he made a "deal with the devil" (Iran), and he gave us another "monstrosity of a social program that was designed to fail". I asked how Obama opened our borders, when did that happen? And the original poster asked if I had been asleep all eight years of the Obama administration. I said I knew he didn't talk about building a wall, but what policies did he implement that "opened our borders"? And he replied that it was not his job to educate me, do the research myself. I did a quick Google search and all that came up was stories about how Obama's DHS secretary recently said that Democratic presidential candidates' proposals to decriminalize border crossing is tantamount to open borders. So then I typed up this question here on SW, and that's all I feel compelled to do to get to the bottom of this. So what did I miss? When and how did Obama roll out the welcome mat to illegal immigrants in between all the deportations he oversaw?

NodandaWink · 51-55, M

@JP1119 They act like that because they have no idea. They are just repeating talking points they've been told and never verified for themselves. In fact Obama deported more illegal immigrants than any of his predecessors. Also catch and release is not a policy but the result of acting on policies which release those seeking assylum, people coming to the border as families or unaccompanied children, on their own recognizance to appear for court when their case is addressed. Obama did not pass those laws they were in existence long before his tenure. Most illegal border crossers are repatriated within days of being apprehended. It is only those with a legal claim for immigration who were so treated. You might find a couple of articles informative.
https://www.factcheck.org/2019/01/trumps-bogus-catch-and-release-statistic/
https://www.vox.com/2018/4/9/17190090/catch-release-loopholes-border-immigrants-trump