Core component of the smc-5/smc-6 complex (PubMed:20661436). Functions in DNA double strand break repair by promoting sister-chromatid homologous recombination during meiosis (PubMed:20661436, PubMed:27011106, PubMed:27010650, PubMed:24424777). Acts in a DNA repair pathway for removal of ionizing radiation- and ultraviolet (UV) radiation-induced DNA lesions that is distinct from classical nucleotide excision repair and the translesion synthesis pathway (PubMed:20661436, PubMed:24424777). Also involved in the recovery of stalled replication forks (PubMed:24424777). Interacts with smc-6. Localizes on chromosomes during diplotene and diakinesis in oocytes. Expressed in the germline (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-6, forming a V-shaped heterodimer. Reduced fecundity and transgenerational sterility (PubMed:20661436). Increased apoptosis in germ cells 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 (PubMed:20661436, PubMed:27010650, PubMed:24424777). Chromosome fragmentation defects and unresolved diakinesis chromosomes in meiotic oocytes (PubMed:20661436, PubMed:27010650). Increased accumulation of homologous recombination intermediates during meiosis (PubMed:20661436, PubMed:27011106, PubMed:27010650). Impaired DNA replication in germ cells (PubMed:24424777). Accumulation of brd-1 and rmh-1 on chromosomes in mitotic germ cells (PubMed:24424777, PubMed:27011106). In a spo-11 mutant background, no accumulation of meiotic rad-51 foci and decrease in chromosome fragmentation (PubMed:20661436). In a him-3 mutant background, increase in 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 xpc-1 mutant background, increased ultraviolet sensitivity (PubMed:24424777). In a xpc-1 or csb-1 mutant background, enhanced ultraviolet-induced delay in somatic development (PubMed:24424777). In a rmh-1 mutant background, increased embryonic lethality and larval arrest (PubMed:27011106). In a him-6 mutant background, increased cross-over frequency, formation of chromatin bridges, defects in diakinetic chiasmata formation, aberrant distribution of the condensin II subunit hcp-6 and compromised chromosome segregation in meiosis, leading to embryonic lethality (PubMed:27010650). Belongs to the SMC family. SMC5 subfamily.