Whenever required by the grand jury, it shall be the duty of the district attorney of the district or his assistant or assistants, to attend them for the purpose of examining witnesses in their presence or of giving them advice in any legal matter, and to issue subpoenas and other process to enforce the attendance of witnesses, and to draw up bills or indictments when found by such grand jury. The district attorney is authorized to issue subpoenas upon his own motion during the grand jury for the purpose of examining witnesses in the presence of the grand jury and the district attorney is further authorized to issue subpoenas upon his own motion for the purpose of examining witnesses before a grand jury that is to be called within ninety days from the issuance of said subpoenas. If, for any reason, the district attorney and all of his assistants are disqualified to act in a particular matter being investigated by the grand jury, the Attorney General of Oklahoma shall appoint one or more Assistant Attorney(s) General or a district attorney or assistant district attorney from another district to act in such matter, as provided in Section 215.9 of this title.