Windows superfetch format
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
- Windows SuperFetch file format – partial specification, by ReWolf, October 5, 2011
- Windows SuperFetch database format, by the libagdb project, April 2014