Difference between revisions of "Windows SuperFetch Format"

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</pre>
 
</pre>
  
The SuperFetch DB files can be stored in uncompressed or compressed form, where different version of Windows use different compression methods:
+
The SuperFetch DB files can be stored in uncompressed or compressed form, where different version of Windows use different compressed forms:
* Compressed SuperFetch DB - MEM file format; Windows Vista and 7
+
* Compressed SuperFetch DB - MEMO file format; Windows Vista
 +
* Compressed SuperFetch DB - MEM0 file format; Windows  7
 
* Compressed SuperFetch DB - MAM file format; Windows 8
 
* Compressed SuperFetch DB - MAM file format; Windows 8
  
=== Compressed SuperFetch DB - MEM file format ===
+
=== Compressed SuperFetch DB - MEMO file format ===
 
The MEM file consists of:
 
The MEM file consists of:
 
* file header
 
* file header
 
* compressed blocks
 
* compressed blocks
 +
 +
This format uses the LZNT1 compression method
  
 
==== File header ====
 
==== File header ====
Line 38: Line 41:
 
| 0
 
| 0
 
| 4
 
| 4
| "MEMO" (0x4d, 0x45, 0x4d, 0x4f) <br> "MEM0" (0x4d, 0x45, 0x4d, 0x30)
+
| "MEMO" (0x4d, 0x45, 0x4d, 0x4f)
 
| Signature
 
| Signature
 
|-
 
|-
Line 48: Line 51:
 
|}
 
|}
  
Where:
+
==== Compressed blocks ====
* "MEMO" (0x4d, 0x45, 0x4d, 0x4f) is used on Windows Vista and uses the LZNT1 compression method
+
The compressed block size is the chunk data size, which is part of the LZNT1 compressed data, + 2 bytes for the size of the chunk header itself.
* "MEM0" (0x4d, 0x45, 0x4d, 0x30) is used on Windows 7 and uses the LZXPRESS Huffman compression method
+
 
 +
The uncompressed block size is 4096 (0x1000) or the remaining uncompressed data size for the last block.
 +
 
 +
=== Compressed SuperFetch DB - MEM0 file format ===
 +
The MEM file consists of:
 +
* file header
 +
* compressed blocks
 +
 
 +
This format uses the LZXPRESS Huffman compression method
 +
 
 +
==== File header ====
 +
The file header is 8 bytes of size and consists of:
 +
{| class="wikitable"
 +
|-
 +
! Offset
 +
! Size
 +
! Value
 +
! Description
 +
|-
 +
| 0
 +
| 4
 +
| "MEM0" (0x4d, 0x45, 0x4d, 0x30)
 +
| Signature
 +
|-
 +
| 4
 +
| 4
 +
|
 +
| Uncompressed (total) data size
 +
|-
 +
|}
  
 
==== Compressed blocks ====
 
==== Compressed blocks ====
Line 76: Line 108:
  
 
=== Compressed SuperFetch DB - MAM file format ===
 
=== Compressed SuperFetch DB - MAM file format ===
On Windows 8 (seen on 8.1) the MEM file format seem to have been replaced by the MAM file format.
+
The MAM file consists of:
 +
* file header
 +
* compressed blocks
  
==== File header ====
+
This format uses the LZXPRESS Huffman compression method.
<b>TODO</b>
+
  
 +
==== File header ====
 +
The file header is 12 bytes of size and consists of:
 
{| class="wikitable"
 
{| class="wikitable"
 
|-
 
|-
Line 92: Line 127:
 
| "MAM\x84" (0x4d, 0x41, 0x4d, 0x84)
 
| "MAM\x84" (0x4d, 0x41, 0x4d, 0x84)
 
| Signature
 
| Signature
 +
|-
 +
| 4
 +
| 4
 +
|
 +
| Uncompressed (total) data size
 +
|-
 +
| 8
 +
| 4
 +
|
 +
| Unknown (checksum?)
 
|-
 
|-
 
|}
 
|}
  
 
==== Compressed blocks ====
 
==== Compressed blocks ====
<b>TODO</b>
+
The uncompressed block size is 65536 (0x10000) or the remaining uncompressed data size for the last block.
 +
 
 +
Note the LZXPRESS Huffman variant used differs from the one used in the MEM0 format. This variant can refer to uncompressed data stored in the previous compressed block. The compressed blocks are essentially a single compressed stream.
  
 
=== Uncompressed SuperFetch DB format ===
 
=== Uncompressed SuperFetch DB format ===
 
<b>TODO</b>
 
<b>TODO</b>
  
 +
==== File header ====
 +
<b>TODO</b>
 +
 +
{| class="wikitable"
 +
|-
 +
! Offset
 +
! Size
 +
! Value
 +
! Description
 +
|-
 +
| 0
 +
| 4
 +
| 0x0000000e
 +
| Unknown (Database type or signature?)
 +
|-
 +
| 4
 +
| 4
 +
|
 +
| Uncompressed (total) data size
 +
|-
 +
|}
 
== TRX files ==
 
== TRX files ==
 
The <tt>Ag*.db.trx</tt> files are of the TRX file format. E.g.
 
The <tt>Ag*.db.trx</tt> files are of the TRX file format. E.g.
Line 157: Line 225:
  
 
== External Links ==
 
== External Links ==
* [http://technet.microsoft.com/en-us/magazine/2007.03.vistakernel.aspx Inside the Windows Vista Kernel: Part 2], by [[Mark Russinovich]], March 2007
 
 
* [http://blog.rewolf.pl/blog/?p=214 Windows SuperFetch file format – partial specification], by ReWolf, October 5, 2011
 
* [http://blog.rewolf.pl/blog/?p=214 Windows SuperFetch file format – partial specification], by ReWolf, October 5, 2011
 +
* [https://googledrive.com/host/0B3fBvzttpiiSWFFkSTBOUHdjOVU/Windows%20SuperFetch%20(DB)%20format.pdf Windows SuperFetch database format], by the [[libagdb| libagdb project]], April 2014
  
 
[[Category:File Formats]]
 
[[Category:File Formats]]

Latest revision as of 18:00, 13 June 2015

Information icon.png

Please help to improve this article by expanding it.
Further information might be found on the discussion page.

SuperFetch, is a memory management scheme that enhances the least-recently accessed approach with historical information and proactive memory management. [1]

Note that the following format specification are incomplete.

SuperFetch DB files

The Ag*.db files are of the SuperFetch file format. E.g.

AgAppLaunch.db
AgCx_SC*.db
AgGlFaultHistory.db
AgGlFgAppHistory.db
AgGlGlobalHistory.db
AgGlUAD_%SID%.db
AgGlUAD_P_%SID%.db
AgRobust.db

The SuperFetch DB files can be stored in uncompressed or compressed form, where different version of Windows use different compressed forms:

  • Compressed SuperFetch DB - MEMO file format; Windows Vista
  • Compressed SuperFetch DB - MEM0 file format; Windows 7
  • Compressed SuperFetch DB - MAM file format; Windows 8

Compressed SuperFetch DB - MEMO file format

The MEM file consists of:

  • file header
  • compressed blocks

This format uses the LZNT1 compression method

File header

The file header is 84 bytes of size and consists of:

Offset Size Value Description
0 4 "MEMO" (0x4d, 0x45, 0x4d, 0x4f) Signature
4 4 Uncompressed (total) data size

Compressed blocks

The compressed block size is the chunk data size, which is part of the LZNT1 compressed data, + 2 bytes for the size of the chunk header itself.

The uncompressed block size is 4096 (0x1000) or the remaining uncompressed data size for the last block.

Compressed SuperFetch DB - MEM0 file format

The MEM file consists of:

  • file header
  • compressed blocks

This format uses the LZXPRESS Huffman compression method

File header

The file header is 8 bytes of size and consists of:

Offset Size Value Description
0 4 "MEM0" (0x4d, 0x45, 0x4d, 0x30) Signature
4 4 Uncompressed (total) data size

Compressed blocks

The file header is followed by compressed blocks:

Offset Size Value Description
0 4 Compressed data size
4 ... Compressed data

The uncompressed block size is 65536 (0x10000) or the remaining uncompressed data size for the last block.

Compressed SuperFetch DB - MAM file format

The MAM file consists of:

  • file header
  • compressed blocks

This format uses the LZXPRESS Huffman compression method.

File header

The file header is 12 bytes of size and consists of:

Offset Size Value Description
0 4 "MAM\x84" (0x4d, 0x41, 0x4d, 0x84) Signature
4 4 Uncompressed (total) data size
8 4 Unknown (checksum?)

Compressed blocks

The uncompressed block size is 65536 (0x10000) or the remaining uncompressed data size for the last block.

Note the LZXPRESS Huffman variant used differs from the one used in the MEM0 format. This variant can refer to uncompressed data stored in the previous compressed block. The compressed blocks are essentially a single compressed stream.

Uncompressed SuperFetch DB format

TODO

File header

TODO

Offset Size Value Description
0 4 0x0000000e Unknown (Database type or signature?)
4 4 Uncompressed (total) data size

TRX files

The Ag*.db.trx files are of the TRX file format. E.g.

AgCx_SC*.db.trx

Note that the following format specification is incomplete.

File header

The file header is variable of size and consists of:

Offset Size Value Description
0 4 1 Unknown (Version?)
4 4 Unknown
8 4 File size
12 4 Maximum number of records (of the record offsets array)
16 4 Number of records
20 ... Record offsets array, where the record offset is a 32-bit integer. Unused record offset are set to 0.

Record

TODO describe

See Also

External Links