Fidelity Investments racked up defined contribution commitments in the first half of the year totaling 315,000 participants, 269 plans and $17 billion in assets under administration, the company says.

The results are not surprising: Fidelity is the dominant DC record keeper, with assets under administration of about $914 billion as of the end of August. And plan sponsors of late have been open to changing custodians, says Christie White, a principal with Cogent Research.

“It’s not a Fidelity-centric issue,” she said.

In a Cogent survey conducted in the spring, 35% of plan sponsors said they intended to put their plan up for review in the next year, and 42% said they planned to do so within the next two years, she explained.

“In previous years, we saw a lot of tinkering with plans--changing eligibility requirements or smaller things,” White said. “That has kind of died down, and they are thinking more of the wholesale changes they can make.”

Of Fidelity’s $17 billion in new assets, more than $15 billion comes from clients who are new to Fidelity; the balance comes from merger and acquisition activity with existing clients, the company said. Fidelity also announced that sales commitments for 2012 have already exceeded more than $6 billion.

A big factor in Fidelity’s success has been the growing complexity of the regulatory environment, including new fee-disclosure requirements, according to Steve Patterson, executive vice president of sales for workplace investing at the company.

“From a regulatory perspective, sponsors are reviewing and making sure they’re with a provider who’s in the business for the long haul,” he said.

Fidelity reported strong sales increases in the emerging, mid, large and tax-exempt markets. Tax-exempt sales, in particular, rose significantly over last year; Fidelity continued to make investments in this sector to support health care and higher education markets as they looked to consolidate providers, the company said.

Sponsors who are shopping their plans are often seeking cost reduction and better service: The Cogent survey revealed that 17% would switch providers based on cost, and 15% based on service. By service, sponsors mean having a partner to handle plan participants’ concerns so that the employer does not have to.

“And as plans get larger, that type of support gets more important,” she said.