I searched the Irish Family History Foundation's database. It contains 12,000,000 surviving rcds for abt 65% of Irish counties. Rcds are increasingly sparse B4 1840, rare B4 1800.
Note 1 - Without a KNOWN parish, the chance of an ancestor's rcds NOT being in this database is AT LEAST 35%.
Note 2 - Only 1/2 of Co. Cork's rcds are in this database.
Note 3 - The RC church kept control over most parish rcds from Tipperary (north). These are ONLY available thru the Tipperary Family History Research center at a substantial fee (regardless of outcome).
For Jacob O'Berry B ???? somewhere in Ireland with the father's forename unknown, I found 4 B rcds: 1847 Tipperary, 1871 Tipperary, 1873 Tipperary, and 1877 Wicklow. One of these MAY be for your ancestor.
B/M/D registration was civil after 1863. Civil rcds, if they survived the 1922 Four-Courts Fire, are kept by the General Register Office. Contact it at http://www.groireland.iehttp://www.groireland.ie for certificat copies.
Google the Foundation's name to lead you to this database. Register, opt to be notified as rcds are added and browse. Pls post your search results to my genforum msg.