*127 OPINION OF THE COURT
Williаm Hinton filed this action more than seven years ago seeking the release of FBI documents pertaining to him under the Freedom of Information Act. Because the FBI withheld all or portions of a large number of the documents requested, the district court directed the FBI to prepare a Vaughn index, a detailed index correlating each withheld item with the statutory justification. The FBI appeals. We must determine as an initial matter whether we have jurisdiction over its appeal.
I.
Background
Hinton is an author and agricultural expert who has been particularly interested in the People’s Republic of China throughout his career. He spent at least six years living in that country and returned home in 1953. He has since revisited on numerous occasions and authored many books and articles on China. The FBI has over the years conducted extensive investigation into Hinton’s activities in China, in the Communist Party of Eastern Pennsylvania and Delaware from which he was expelled in 1964, and in various other groups.
In February 1980, Hinton wrote to the FBI invoking the terms of the Freedom of Information Act (FOIA), 5 U.S.C. § 552 (1982), to request any and all records kept by the Bureau concerning him. In the course of the next year, he exhausted the agency process due him under FOIA without securing any documents. On February 23, 1981, Hinton brought this FOIA suit, stating that he needed the requested information for a forthcoming book.
The initial issue before the district court was not whether information had been improperly withheld, but whether the FBI should be ordered to expedite its processing of Hinton’s request. Although the FBI was, as the court noted, “diligently handling plaintiff’s request,” it was faced with a substantial backlog of unfilled FOIA requests.
Hinton v. FBI,
There are 10,462 pages of documents (excluding duplicates) responsive to Hinton’s request. For FOIA purposes, pages of documents must be distinguished from documents. For example, in one case one document consisted of 100 pages.
See Meeropol v. Meese,
According to a breakdown compiled by the FBI, the information sought by Hinton falls into six general categories: 51 percent of the records pertain to Hinton’s activities in China between 1947 and 1953, and to possible perjury and violation of the Foreign Agents Rеgistration Act; 15 percent of the records arose out of monitoring of Hinton’s activities as a member of the Communist Party of Eastern Pennsylvania and Delaware between 1957 and his expulsion in 1964; 4 percent of the material pertains to the FBI’s monitoring of Hinton’s “participation in antiwar activities and his travels about giving pro-Communist Chinese speeches” between 1965 and 1967; about 10 percent of the material was gаthered between 1970 and 1977 on “Hinton’s positions and activities in the Revolutionary Union and the United States-China People’s Friendship Association”; “just over 4 percent of the material is composed of information derived from such public sources as newspapers, magazines and books;” fi *128 nally, about 15 percent of the material is made up of “ ‘See’ references wherein Hinton’s name came to [FBI] attention incident to the investigation of an organization or another person.” App. at 62-65.
Of these documents, 2,204 pages were released in their entirety, 4,916 pages were released in more or less heavily redacted form, and 3,342 pages were entirely withheld. Most redacted and withheld material was assertedly within three FOIA exemptions: exemption 1, protecting national security information, 5 U.S.C. § 552(b)(1); exemption 7(C), protecting law-enforcement investigatory records the release of which would constitute an unwarranted invasion of personal privacy. Id. § 552(b)(7)(C); and exemption 7(D), protecting the identities of confidential law enforcement sources, id. § 552(b)(7)(D).
Hinton then moved the court to order the FBI to prepare an index as first required in
Vaughn v. Rosen,
The FBI appeals. It reads the district court’s opinion as concluding that a modified Vaughn index such as it proposed is never permissible, and argues that such a conclusion is erroneous as a matter of law. Hinton has moved to dismiss the appeal for lack of appellate jurisdiction.
II.
The Vaughn Procedure
An order requiring a federal agency to prepare a
Vaughn
index is designed to balance an individual’s right to disclosure of documents pursuant to FOIA’s underlying purpose of opening government conduct to scrutiny by an informed, active citizenry,
see, e.g., N.L.R.B. v. Robbins Tire & Rubber Co.,
The statutory provision for discretionary
in camera
review of withheld materials by the trial judge, 5 U.S.C. § 552(a)(4)(B);
see
H.R.Rep. No. 876, 93d Cong., 2d Sess. 7,
reprinted in
1974 U.S. Code Cong. & Admin. News 6267, 6273, does not provide a complete solution, because such review may impose a significant burden on the court. The court is also deprived of the illumination to be derived from the requester’s counsel. As the
Vaughn
court observed: “If the morass of material is so great that court review becomes impossible, there is a possibility that an agency could simply point to selected, clearly exempt portions, ignore disclosable sections,
*129
and persuade the court that the entire mass is exempt.”
The Supreme Court first suggested in
EPA v. Mink
that the need for
in camera
review might be obviated by requiring the agency to justify its withholding by detailed affidavits or testimony.
See
There is no set formula for a
Vaughn
index; subsequent decisions from the D.C. Circuit have explained that it is the function, not the form, which is important.
See, e.g., Keys v. United States Dep’t of Justice,
[Ujnder ordinary circumstances a Vaughn index ... will generally suffice to narrow the disputed issues and permit a reasoned disposition by the district court.... In both the ordinary and the exceptional case, in camera affidavits and submissions are authorized and the distriсt court may resort to them in arriving at its ultimate determination. In both instances, the district court must have furnished to it, in whatever form, public or private, all of the detailed justifications advanced by the government for non-disclosure. The government must also give the court an opportunity to review all the materials which the government claims to be exempt, even though the decision whether to inspect these matеrials rests with the district court.
Id. at 922.
III.
Appellate Jurisdiction
It is evident from the foregoing that the district court’s order of a Vaughn index is a means to an end and hence not a final order under 28 U.S.C. § 1291 (1982). Although the district court certified a second appeal under 28 U.S.C. § 1292(b), a panel of this court denied permission to appeal. Despite its failure to obtain the certified interlocutory appeal, the FBI maintains that we have jurisdiction under 28 U.S.C. § 1292(a)(1), the Cohen collаteral order doctrine, or the All Writs Act. We conclude that none of these routes supports this court’s jurisdiction.
A.
28 U.S.C. § 1292(a)(1)
The FBI argues that the district court’s order has the practical effect of an injunction, and that it is immediately appealable because it might have serious, even irreparable consequences which may only be effectively challenged on an immediate appeal.
See Carson v. American Brands, Inc.,
The FBI misperceives the scope of section 1292(a)(1). As one of the cases on which it relies defined the term, an injunction under section 1292(a)(1) encompasses “any order ‘directed to a party, enforceable by contempt, and designed to accord or protect
some or all of the substantive relief sought
by a complaint in more than preliminary fashion.’ ”
IAM Nat’l Pension Fund Benefit Plan A v. Cooper Industries, Inc.,
If the fact that the court has directed a party to take some action, here to produce the index, is enough to constitute the order as an injunction, then every discovery order would qualify for immediate interlocutory appeal under section 1292(a)(1). However, the general non-appealability of discovery orders is well-established.
See, e.g., Cipollone v. Liggett Group, Inc.,
The FBI argues that this case is like
Coastal States
where we held we had appellate jurisdiction under section 1292(a)(1) over the district court’s order directing actual release of the requested documents after it found the government’s
Vaughn
index was fatally deficient. However, in
Coastal States
we noted that the order of the district court “achieved the plaintiff’s very objective — to compel production of documents.”
B.
28 U.S.C. § 1291
The FBI next suggests that the district court’s order falls within that narrow class of collateral orders appealable under the doctrine of
Cohen v. Beneficial Indus
*131
trial Loan Corp.,
The collateral order doctrine is confined to a “small class” of decisions too important to await the conclusion of the case.
Coopers & Lybrand,
Moreover, the order at issue fails to qualify as a collateral order under Cohen because it does not conclusively resolve a disputed issue. The FBI maintains that it doеs, because it reads the district court order as concluding that the court lacked any discretion under Third Circuit precedent to order a modified index. The FBI points to the following footnote in the district court’s order:
The purpose of a Vaughn index is to provide the Court with sufficient information to evaluate government claims that documents requested from an agency pursuant to the [FOIA], 5 U.S.C. § 552, are properly subject to one or more exemptions to the [FOIA’s] general policy of disclosure. Vaughn v. Rosen,484 F.2d 820 (D.C.Cir.1973), cert. den.,415 U.S. 977 [94 S.Ct. 1564 ,39 L.Ed.2d 873 ] (1974). The principles and procedures outlined in Vaughn have been adopted by this Circuit. Lame v. U.S. Dept. of Justice,654 F.2d 917 (3d Cir.1981). Notwithstanding the Federal Bureau of Investigation’s argument that two subsequent decisions from the District of Columbia Circuit permit the production of a truncated Vaughn index consisting of the indexing of only a portion of the documents which the government claims are exempt under [FOIA], the case law in this Circuit provides no justification for such a course. Moreover, we find that thе cases upon which the FBI relies, viz., Weisberg v. U.S. Dept. of Justice, 745 F.2d 1476 (D.C.Cir.1984), Ash Grove Cement Co. v. F.T.C.,511 F.2d 815 (D.C.Cir.1975), do not support its position on this issue under the circumstances of this case. Consequently, we here order a complete and detailed index consistent with the sound principles enunciated in Vaughn and Lame.
Hinton v. FBI, No. 81-0740, slip op. at 4 n. 1 (E.D.Pa. May 7, 1987) (citations omitted).
Although the footnote is not without some ambiguity, we do not read it as signifying that the district court regarded itself as bound to order a full index. 2 Instead, it appears that the district court exercised its discretion to conclude that a partial index was not justified “under the circumstances of this case.”
Our reading of the district court’s action is supported by the fact that the court properly distinguished the cases on which the FBI relied. For example, in
Weisberg
*132
v. United States Dep’t of Justice,
Finally, we read differently than the FBI even the portion of the district court’s order that the FBI argues demonstrates that the district court misread our precedent. In
Lame,
we held that the government had failed to meet its obligation to provide detailed justifications for its claimed exemptions. Judge Garth, writing for the court, noted that one of the purposes of a
Vaughn
index is to “discourage conclusory claims of exemption.”
In short, taking the district court’s order as a whole, it represents the district court's exercise of its discretion to order a Vaughn index, as it stated, “consistent with the sound principles enunciated in Vaughn and Lame.” Hinton, slip. op. at 4. We do not read it tо conclusively determine that our case law forbids the order of a modified Vaughn index in an appropriate case. Under these circumstances, the court’s order cannot be viewed as a Cohen collateral order.
C.
Mandamus
For a similar reason, we also decline the FBI’s suggestion that we exercise our authority to treat the appeal as a petition for a writ of mandamus under the All Writs Act, 28 U.S.C. § 1651 (1982).
See Gold v. Johns-Manville Sales Corp.,
Mandamus is appropriate “to confine an inferior court to a lawful exercise of its prescribed jurisdiction or to compel it to exercise its authority when it is its duty to do so.”
Roche v. Evaporated Milk Ass’n,
It follows that mandamus cannot be used to review the district court's exercise of its discretion.
See Allied Chemical Corp. v. Daiflon, Inc.,
Even if mandamus were available to review a gross abuse of discretion,
see Rodgers,
IV.
Conclusion
For the foregoing reasons, Hinton’s motion to dismiss the appeal for lack of appellate jurisdiction will be granted.
Notes
. We will grant Hinton’s motion to strike the portion of the appendix containing these affidavits which the FBI included in the appendix without notice of any kind to Hinton or the permission of this court. The affidavits were prepared specifically for this appeal, and could not have been part of the record on appeal. We reject the FBI's suggestion that we may take judicial notice of the affidavits pursuant to Fed. R.Evid. 201. That Rule covers only adjudicative facts "not subject to reasonable dispute," that are either “generally known within the territorial jurisdiction of the trial court ... or capable of accurate and ready determination by resort to sources whose accuracy cannot reasonably be questioned.” Hinton vigorously disputes the FBI’s predictions, contained in the affidavits, as to the amount of time required to prepare the requested Vaughn index. He notes, for example, that the FBI calculations are at least 25 percent too high because they are based on 11,000 pages, which includes the 2,656 pages which were deemed to be outside the scope of the plaintiffs request, App. at 173 n. 1, as to which Hinton does not seek an index. Moreover, the FBI has conceded in its affidavit that its predictions are in essence at most estimates "difficult if not impossible to quantify." See App. at 172. This is simply not the type of fact subject to judicial notice.
. Other courts have, on appropriate occasion, ordered indexing of only a sampling of the withheld documents,
see Weisberg v. United States Dep’t of Justice,
