Mac OS X hard drives are generally divided into various volumes. The hard drive volumes may contain four types of items: files, file threads, directories, and directory threads. Every item is identified by the catalog record. Catalog records are formed in on-disk catalog B-Tree. The contents of a directory are derived by exploring the catalog B-Tree. However, if the catalog records are damaged, you can not access the file. Such situations may lead to data loss and will need Mac Recovery to recover all the lost data.
A Mac OS X file has the following two forks or components-
Resource fork- An indexed file that contains menu items, code segments, and dialog boxes.
Data fork- Contains stream of bytes.
Every component is made up of one or more contiguous runs or extents of blocks. Length and starting block of an extent is encoded by an extent descriptor in 32bit quantity. First extent record of every component is the part of catalog record of the file.
Along with the B-Tree extents and files, a Mac OS X hard drive volumes also include two boot blocks – volume information block and free space bitmap. In order to improve the crash recovery abilities, a remarkable amount of redundancy of disk data structures is maintained. While not necessarily the part of file system, several catalog records are reserved for exclusive use of the Finder application.
Each file and folder on Macintosh volume has a unique identification number. Still, files or directories are named by the identification number of their parent file or file name of the directory. This combination is used as a search key for catalog B-Tree of the volume.
Under some circumstances, the catalog record or catalog B-Tree may get damaged due to virus infection, file system errors, improper system shutdown, and other similar reasons. In such cases, you may encounter error message similar to the following, while trying to access the file:
“Message Catalog System: corrupt file”
This behavior may render the files inaccessible and need Data Recovery Mac to retrieve the inaccessible files.
Mac Data Recovery is possible using advanced and powerful third-party Mac Recovery Software. They carry out extensive scan of the affected Mac OS X hard drive volume and extract all lost, missing, and inaccessible files from it. The applications enable safe, quick, and easy recovery in all data loss situations.
Stellar Phoenix Macintosh Data Recovery is an excellent solution to ensure absolute recovery of your lost Mac data. The software is designed for Mac OS X 10.6 Snow Leopard, 10.5 Leopard, 10.4 Tiger, and 10.3.9 Panther. It supports recovery from HFS, HFS+, HFSX, HFS Wrapper, and FAT file system volumes.
