error hibernate failed to lazily initialize a collection of role

failed to lazily initialize a collection of role: com.ipi.bean.Dologs.DtldologsSet, no session or session was closed

q> Waw error ketika nambahin @OneToMany pada header Dologs

q> @ManyToOne
[sourcecode language="java"]
@JoinColumn(name="DTL_NO_DOLOG", referencedColumnName="HDR_NO_DOLOG", insertable = false, updatable = false)
@ManyToOne(cascade=CascadeType.ALL)
private Dologs dologs;
[/sourcecode]

q> Sebelumnya

[sourcecode language="java"]
@OneToMany(mappedBy="dologs")
private Set<TrioH100Dtldologs> dtlDologsSet;
[/sourcecode]

q> Sesudah ditambahin fetch=FetchType.EAGER , error menghilang

[sourcecode language="java"]
@OneToMany(fetch=FetchType.EAGER,mappedBy="dologs")
private Set<TrioH100Dtldologs> dtlDologsSet;
[/sourcecode]