| 摘要 |
<p>A word processing system is disclosed in which a text stream is stored on a direct access storage device (DASD) for recall and editing. The text stream is organized into a document, which is stored on the DASD as a data set. The data set consists of an index portion and a portion containing text records. The index portion is divided into nodes, of which the primary node is called the root node.</p><p>A method called shadowing, involving redundant recording (425-438) of critical index nodes with almost no penalty in increased data set index size, is introduced to protect (402-414) those index nodes the loss of which would mean significant loss of data to the system operator.</p><p>Status indicators (395, 304) at the data set and volume level are defined and maintained so that access to a data set for normal system operations may be prevented when there is a significant chance that the data set index has errors or is inconsistent to the extent that the normal high-performance access method routines may not be able to use the index or may cause inadvertent loss of valid text data for the system operator.</p><p>Finally, recovery mechanisms (525-540) are disclosed in which all of the data on the volume that can possibly be located by means of volume and data set indexes is restored for operator use after abnormal terminations during complex data set index updates or when intermediate nodes in large data sets are lost due to storage media input physical errors.</p> |
