Striking port clerks on Wednesday shut down most container terminals at the local ports. Three of six terminals at the Port of Long Beach remain open, while just one of seven terminals is open at the Port of Los Angeles.

The strike by office clerks, members of the International Longshore and Warehouse Union’s Local 63 Office and Clerical Unit, or OCU, has now become the largest strike at the port in a decade. It began Tuesday at a single terminal in Los Angeles and spread Wednesday afternoon. Longshore workers are honoring the clerical workers’ picket lines.

The longshore action came despite a Tuesday ruling by a local labor arbitrator who said they should not honor the pickets. That ruling has been appealed to an arbitrator who oversees labor issues for all West Coast ports.

Representatives for the union and the Los Angeles/Long Beach Harbor Employers Association, a trade group that represents most of the twin ports’ terminal operators, were meeting with the West Coast arbitrator Wednesday.

The terminals that remain open are operated by TraPac Inc. and SSA Marine, which are not members of the employers association.

The OCU and harbor employers have been negotiating for more than two years. The most recent contract expired in July 2010. The main sticking point between the two sides has been job security, with the employers saying they have offered complete security to current workers and the union saying employers are trying to send clerical jobs overseas. The OCU represents about 800 workers.