Mac OS X system comprise of hard disks divided into volumes, each comprising of items namely files and file threads, directories and directories threads. Each of these volume information is organized in a catalog files, structured as B* tree. Catalog files of Mac system is one of the system file and the HFS i.e. Hierarchial File System's file manager. These account for system's most significant data store as details concerning file & directory hierarchy is also comprised within it.

The B tree structured catalog file in turn include 4 different nodes as – header, leaf, index and map. The nodes are assigned specific number also called as CNID, that helps with location of data from the volume. Whenever a volume is to be located & mounted system navigates through the node & structure so as to find the directory information necessary to have access to data items within.

However, when these trees or its nodes encounter problems the system may not be able to function properly and locate files & folders thereoff. This is the time system would generate fatal errors, accounting to corruption of file system structure, giving error message as -

“Verifying volume
Checking HFS Plus volume.
Invalid record count
Invalid record count
Catalog file entry not found for extent
The volume needs to be repaired.”

In state as this, it is of essential importance to have the structures repaired. Such are the situations in which all the system data is made inaccessible for users and while trying to have access to volumes or have its integrity checked with disk utility so as to get it repaired, it is likely to show error messages as -

“Invalid B-tree node Size”

Here in the situation disk damages aren't repairable with disk utility, leading to acute data loss problem which could only be tackled, provided one has an updated backup for the very purpose.

How to fix Catalog file corruption -catalog file entry not found for extent?

As disk utility is mostly found to fail in repairing mac catalog file errors, using FSCK repair in single mode, in most of the situations is recommended. Though, its failure would require use of other repair utilities that may be available for the purpose.

On the other side to get rid of all mac catalog file corruption issues and efficiently perform Mac catalog file corruption recovery, clean reinstall of Mac OS X or system formatting is usually done. It helps users in mac catalog file corruption recovery in all instances as the process is all about creation of new file system & structure post removal of the previous or the damaged ones.

Though the disadvantage here is that of loss of data from the drives as well, as formatting does remove all those from the hard disk or make it empty. In the process of this data unavailability file recovery mac software is to be used that help restore files from damaged, corrupt, formatted and inaccessible Mac volumes with much ease & efficiency as also supports different Macintosh OS X viz. 10.4, 10.5, 10.6 and 10.7.