Guanine nucleotide exchange factor (GEF) that activates monomeric GTPases by catalysing the release of bound GDP in exchange for free GTP (PubMed:32651375). Activates RAC1 and RAC2, but not CDC42 (PubMed:21613211, PubMed:32651375). Involved in cytoskeletal rearrangements required for lymphocyte migration in response of chemokines (PubMed:21613211). May also participate in IL2 transcriptional activation via the activation of RAC2 (PubMed:21613211). {ECO:0000269|PubMed:21613211, ECO:0000269|PubMed:32651375}. This is the function of ENSG00000134516 (DOCK2, dedicator of cytokinesis 2).