Reorganization and repair of an icf catalog while open and in-use in a digital data storage system

Abstract

MVS mainframe computer systems employ the ICF (Integrated Catalog Facility) catalog environment to manage numerous data sets. To provide nearly continuous availability of those data sets, the BCS catalog ( 250,270 ) must be re-organized while leaving the catalog open to access by applications. To perform a re-org while open, a data CI correlation table ( 500 ) can be constructed ( 314 ) and used to lay the data CIs into a backup file in logical order ( 316 ), so that they can be loaded into the new BCS catalog ( 324 ) without sorting, thereby reducing downtime.

1 . A computer-implemented data structure stored in machine-readable memory for use in re-organizing or restoring an ICF catalog in a VSAM mainframe storage environment, the data structure comprising: 
 a correlation table having a series of entries, each entry corresponding to a physical CI number in a BCS data component; and    wherein each entry in the table contains a first pointer to a CI containing lower keys and a second pointer to a CI containing higher keys, so that the table contents together form a logical list of the CIs.    
   
   
       2 . The computer-implemented data structure of  claim 1  wherein a predetermined value is used in the table to indicate an end of a chain of key values.  
   
   
       3 . The computer-implemented data structure of  claim 1  wherein a predetermined pointer value is used in the table to indicate an empty data CI.  
   
   
       4 . The computer-implemented data structure of  claim 1  wherein a predetermined pointer value is used in the table to indicate an end of a chain of key values.  
   
   
       5 . The computer-implemented data structure of  claim 1  wherein each entry further includes a backward pointer.  
   
   
       6 . The computer-implemented data structure of  claim 1  wherein each table entry that does not correspond to a data CI containing the high key includes a forward pointer identifying a data CI having a next key in a predetermined key sequence.  
   
   
       7 . A data structure stored in machine-readable memory for storing a correlation between a number of logical keys of a BCS data set and one or more respective physical locations of the data set, for use in reorganizing the BCS while open.  
   
   
       8 . A data structure according to  claim 7  wherein the data structure is comprised of a table for storing a correlation between the logical order of the data CIs of a BCS data set and the physical location of the data CIs, for use in reorganizing the BCS while open.  
   
   
       9 . A data structure according to  claim 7  wherein the correlation comprises a correlation between the logical order of the keyed records of a BCS data set and the respective data CIs that contain them.  
   
   
       10 . A logical CI correlation table stored in machine-readable memory for use in re-organizing or restoring an ICF catalog in a VSAM storage environment, the correlation table comprising: 
 a series of entries, each entry corresponding to a physical CI number in the BCS data component; and    each entry including a first pointer to a CI containing lower keys and a second pointer to a CI containing higher keys, so that the table contents together form a logical list of the CIs.    
   
   
       11 . A correlation table for use in re-organizing an ICF catalog in a VSAM storage environment, the correlation table comprising: 
 a series of entries, each entry corresponding to one of the data CI's in the catalog, and wherein each entry in the table comprises a forward pointer to support reading the data records in key sequence.    
   
   
       12 . A correlation table according to  claim 11 , wherein a predetermined value is used in the table to indicate either end of a chain of key values.  
   
   
       13 . A correlation table according to  claim 11 , wherein a predetermined pointer value is used in the table to indicate an empty data CI.  
   
   
       14 . A correlation table according to  claim 11 , wherein a predetermined pointer value is used in the table to indicate an end of a chain of key values.  
   
   
       15 . A correlation table according to  claim 11 , wherein each entry further includes a backward pointer.  
   
   
       16 . A correlation table according to  claim 11 , wherein each table entry that does not correspond to a data CI containing the high key includes a forward pointer identifying the data CI having a next key in a predetermined key sequence.  
   
   
       17 . A computer-implemented method of reorganizing an ICF catalog comprising a key sequential data set (KSDS) BCS in a VSAM system while the catalog is open, the BCS comprising a data component and an index component, the reorganization method comprising the steps of: 
 (a) the catalog with exclusive control;    (b) creating a backup of the index component;    (c) based on sequence set records of the index component, determining, for each data CI in a data set, a physical location of the CI in the data component and a logical location of the CI in key sequence order;    (d) reading data CIs from the data component out to an internal backup data set in potential logical key sequence order so as to form an ordered backup of the data without sorting;    (e) clearing all data CI's in the data component and clearing the index component;    (f) updating the BCS VSAM control blocks so as to reflect an empty BCS;    (g) reloading the data set from the ordered backup, sorting records if necessary, and using standard VSAM I/O to reload the data records and reconstruct the index; and    (h) closing the catalog so as to update VVRs in the VVDS and re-sync it with CAS.