You may sometimes find that files or directories have been completely lost due to disk corruption.

If after running chkfsys, you know that certain key files or directories weren't recovered, then you might be able to use spatch to recover some or all of this data.

The spatch utility lets you browse the raw disk and patch minor problems. You can sometimes cure transient disk problems by reading and writing the failing block with spatch.

Note: Before using spatch, make sure you understand the details of a QNX 4 filesystem; see "QNX 4 disk structure" earlier in this chapter.