The VERIFY command is used to verify, and if necessary, to update, the end of file information in the VSAM catalog in order to make the catalog information consistent with the data file.
The VERIFY command cannot be used for an empty VSAM file where the high used RBA (Relative Byte Address) in its catalog record is 0 (zero).
The creation of a low value record in an empty VSAM file is normally the first step VSAM performs after a file is defined.
When a VSAM dataset is closed in an update program, VSAM will update the end of file information in both the VSAM catalog and the data file.
If an update program fails or the operating system fails, VSAM may not close the file properly. When this happens, VSAM is unable to update important information in the file's catalog record.
The VSAM file's catalog record has the high used RBA that specifies the end of the file address. If this field is not updated, the information stored in the catalog record does not agree with the actual contents of the related file.
After the abnormal termination of a VSAM file, the VERIFY command must be executed to correct the catalog record information to reflect the actual status of the dataset before the file is used again.
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