Reorganization and repair of an ICF catalog while open and in-use in a digital data storage system
View Patent ↗MVS mainframe computer systems employ the ICF (Integrated Catalog Facility) catalog environment to manage numerous data sets. To provide 24×7 availability of those data sets, the BCS ( 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 ) is 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 ( 324 ) without sorting, thereby reducing downtime. Additionally, if the BCS is damaged during normal operation, repair of the structure must also be performed to ensure that correct access is maintained to all data that is cataloged in the BCS. Throughout the re-org process, structural integrity checks are performed on the data and index component of the BCS, and if errors are encountered, they can be repaired.
1. 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) opening the catalog with exclusive control;
(b) creating a backup of the index component;
(c) using a number of sequence set records of the index component, constructing a logical CI correlation table, the table indicating, for each data CI in the data set, a physical location of the CI in the data component and a logical location of the CI in key sequence order;
(d) using the logical CI correlation table, 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 CIs in the data component and clearing the index component;
(f) updating 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 to update VVRs in a VVDS and re-sync the catalog with CAS.
2. The computer-implemented method according to claim 1 wherein the logical CI correlation table is constructed in random access storage.
3. The computer-implemented method according to claim 1 wherein the reloading step includes applying the original free space attributes of the BCS.
4. The computer-implemented method according to claim 1 and further comprising creating an ESTAE environment prior to said creating a backup of the index component, and terminating the ESTAE environment after said reloading step.
5. The computer-implemented method according to claim 1 and further comprising checking for errors during the reloading step and, if an error is detected, recovering the catalog to its pre-reorganization state.
6. The computer-implemented method according to claim 5 and wherein said recovering step comprises copying index and data CIs from the internal backup into the BCS physical locations indicated in the internal backup, thereby restoring the index and data component to the pre-reorganization state.
7. A method of stabilizing an ICF catalog in a VSAM system preparatory to re-organizing the catalog, the method comprising the steps of:
(a) issuing an instruction to obtain a first timestamp;
(b) reading a number of BCS VVR records to obtain the latest BCS refresh timestamp;
(c) opening the BCS with a standard VSAM OPEN macro;
(d) issuing a RESERVE macro for a SYSIGGV2 resource name, to obtain exclusive control of the catalog;
(e) obtaining VVRs for the data and index components of the BCS from a VVDS on a volume where the BCS resides;
(f) comparing the first timestamp to the latest BCS refresh timestamp stored in the BCS's data component VVR; and
(g) if the latest BCS refresh timestamp is greater, repeating the foregoing steps (a) through (f), inclusive, until the latest BCS refresh timestamp is equal or less than the timestamp obtained prior to the latest iteration of the step (c) opening process.
8. The computer-implemented method according to claim 1 and further comprising an initial step of stabilizing the catalog.
9. The computer-implemented method according to claim 8 wherein stabilizing the catalog comprises the steps of:
(a) issuing an instruction to obtain a first timestamp;
(b) reading a number of BCS WR records to obtain the latest BCS refresh timestamp;
(c) opening the BCS with a standard VSAM OPEN macro;
(d) obtaining VVRs for the data and index components of the BCS from a VVDS on a volume where the BCS resides;
(e) comparing the first timestamp to the latest BCS refresh timestamp stored in the BCS's data component VVR; and
(f) if the latest BCS refresh timestamp is greater, repeating the foregoing steps (a) through (e), inclusive, until the latest BCS refresh timestamp is equal or less than the timestamp obtained prior to the latest iteration of the step (c) opening process.
10. The computer-implemented method according to claim 1 wherein opening the catalog with exclusive control comprises issuing a RESERVE macro for a SYSIGGV2 resource name.