Core component of the smc-5/smc-6 complex (PubMed:20661436). Involved in DNA double-strand break repair by promoting sister-chromatid homologous recombination during meiosis (PubMed:20661436, PubMed:24939994, PubMed:27010650). Also plays a role in the DNA damage repair of ultraviolet (UV) radiation-induced DNA lesions (PubMed:24424777). Promotes efficient DNA replication (PubMed:24424777). Interacts with smc-5. Nucleoplasmic in the distal gonad arm and localizes on chromosomes during pachytene, diplotene and diakinesis in oocytes. Expressed in the germline (at protein level). Expressed in the primordial germ cells Z2 and Z3 in embryos and in proliferating germ cells in L2/L3 stage larvae (at protein level). The flexible hinge domain, which separates the large intramolecular coiled coil regions, allows the heterotypic interaction with the corresponding domain of smc-5, forming a V-shaped heterodimer. Reduced fecundity and transgenerational sterility (PubMed:20661436). Increased germ cell apoptosis and hypersensitivity to ultraviolet and ionizing radiation and hydroxyurea-induced replication stress (PubMed:20661436, PubMed:24424777). Increased rad-51 foci in the mitotic and meiotic germline on autosomes, but not on X chromosomes (PubMed:20661436, PubMed:27010650, PubMed:24424777, PubMed:24939994). Chromosome fragmentation defects and unresolved diakinesis chromosomes in meiotic oocytes (PubMed:20661436, PubMed:27010650). Impaired DNA replication in germ cells (PubMed:24424777). Accumulation of brd-1 on chromosomes in mitotic germ cells (PubMed:24424777). In a him-3 mutant background, increased rad-51 foci and chromosome fragmentation (PubMed:20661436). RNAi-mediated knockdown of syp-2 leads to an increase of chromosome fragmentation (PubMed:20661436). In a him-6 mutant background, leads to synergistic lethality (PubMed:27010650). In a fem-3 or him-8 mutant background, RNAi-mediated knockdown leads to increased fragmentation of autosomes and asynapsed X chromosomes but not of X chromosomes in males (PubMed:24939994). Belongs to the SMC family. SMC6 subfamily.