When a user program closes a VSAM data set, the system uses the data set's end-of-data information to update its cataloged information. If a system failure occurs before the user program closes the data set, its cataloged information is not updated and any records in unwritten buffers are not written to the data set.

If an error occurs while a component is opened for update processing, it can improperly close (leaving the open-for-output indicator on). At OPEN, VSAM implicitly issues a VERIFY command when it detects an open-for-output indicator on and issues an informational message stating whether the VERIFY command is successful.

When the last CLOSE for a VSAM data set completes successfully, VSAM turns off the open-for-output indicator. If the data set is opened for input, however, VSAM leaves the open-for-output indicator on. It is the successful CLOSE after an OPEN for output that causes the open-for-output indicator to turn off. Before you use any data set that was not successfully closed, determine the status of the data in the data set. Turning off the open-for-output indicator in the catalog does not make the data set error free.