How to update child table data using parent reference in eclipselink?

[kamesh vadam]

private Integer space;

@OneToMany(mappedBy = "userid",cascade = CascadeType.PERSIST)
private Collection<Externalstoragecredentials> externalstoragecredentialsCollection;

this is parent entity

@JoinColumn(name = "userid", referencedColumnName = "id")
@ManyToOne(cascade = CascadeType.PERSIST)
private Dpatchuser userid;

this is child entity

can you give named query to update child table data.