Abstract: A method, apparatus, and article of manufacture for providing transaction control for a computer-implemented database management system. The database management system manages one or more databases, wherein each of the databases contains one or more documents and each document contains one or more objects. The database management system also supports a file cache for those databases. A transaction control system provides transaction control for the databases, documents, and objects managed by the database management system, wherein the transaction control system monitors and controls the file cache to ensure that modified objects are stored on a data storage device in manner that reflects an accurate status for a log file maintained by the transaction control system.

Abstract: A data manager of a relational database management system (RDBMS) receives a command, such as a DELETE. As the RDBMS processes this command, an index manager looks at cursor control block information about the scan position (page number, logical key position within page and log sequence number (LSN) of the page) and immediately accesses the corresponding leaf page to do the key deletion. If the page's log sequence number has not changed since the scan was positioned on it, the index manager knows precisely where the key is and deletes it right away. Even if the page's log sequence number has changed, the index manager checks to see if the key is still on the same page. Only if the key is not on that page anymore will the index manager traverse the tree from the root to locate the key. Using this same information, together with a return.sub.-- current flag in the cursor control block, the method can easily determine the next key in the sequence. The return.sub.

Abstract: A multi-tiered indexing method is disclosed for a partitioned table in a parallel or distributed database system. A Local Index is created and maintained for each partition of the table and a Coarse Global Index is created and maintained. The Coarse Global Index identifies the indexed partition(s) by partition identifiers (PIDs) and associates the individual Index Key Values with their target partitions so that an access request with a highly partition-selective search predicate on the Index Key can be quickly and easily directed to the target partition(s) for processing. An index maintenance locking protocol is also disclosed which handles the insertion and deletion of index entries and assures the consistency between the Local Index entries and the Coarse Global Index entries during concurrent index accesses by different transactions.

Abstract: A computer-implemented method for minimizing the amount of time to access current data in a database which may be stored wholly in a DASD-oriented external storage subsystem or partly in DASD and partly in a stored high-speed electronic store while maintaining coherency of the data with respect to multiple user systems.

Abstract: A computer program product, such as a pre-recorded software program on a floppy disk, is disclosed, for use with a processing and database system for off-loading, to disk controller, the extraction of committed data. Responsive to the pre-recorded program instructions, the system first picks a Commit.sub.-- LSN value and insures all the data modified prior to the Commit.sub.-- LSN value is processed following the DBMS policy of reducing some disk I/Os or not for the modified pages cached in the system. If the policy is not to do disk I/Os for such pages, then the system places the identifiers of those pages in an ignore list. Otherwise, the system writes those pages to disk and empties the ignore list. Afterwards, the system forwards the ignore list and the Commit.sub.-- LSN along with information regarding the data to be processed to the controller.

Abstract: A computer-implemented method for minimizing the amount of time to access current data in a database which may be stored wholly in a DASD-oriented external storage subsystem or partly in DASD and partly in a stored high-speed electronic store while maintaining coherency of the data with respect to multiple user systems.

Abstract: A computer database system utilizes a method for performing a right outer join of database tables without sorting the inner table (T.sub.2). The processing of each tuple in the outer table (T.sub.1) includes the preservation in the joint output of all tuples in T.sub.2 which are in its responsibility region. The initialization step of the process preserves in the join output all of the tuples in T.sub.2 which have column set values less than the lowest column set value in T.sub.1, i.e. the first tuple in T.sub.1, since T.sub.1 is sorted or accessed using a sorted index. The responsibility region for tuples in T.sub.1, other than the last tuple, is defined as those tuples which have column set values less than the column set value for the next tuple in T.sub.1 and greater than or equal to the column set value for the current T.sub.1 tuple. The last tuple in T.sub.1 must preserve all of the tuples in T.sub.2 which have not already been preserved in T.sub.2, i.e.

Abstract: A multi-tiered indexing method is disclosed for a partitioned table in a parallel or distributed database system. A Local Index is created and maintained for each partition of the table and a Coarse Global Index is created and maintained. The Coarse Global Index identifies the indexed partition(s) by partition identifiers (PIDs) and associates the individual Index Key Values with their target partitions so that an access request with a highly partition-selective search predicate on the Index Key can be quickly and easily directed to the target partition(s) for processing. An index maintenance locking protocol is also disclosed which handles the insertion and deletion of index entries and assures the consistency between the Local Index entries and the Coarse Global Index entries during concurrent index accesses by different transactions.

Abstract: In a combination of multiple concurrently-executing database management systems which share data storage resources, efficient lock processing for shared data is implemented by hiding from a global lock manager the distinction between transaction-interest and cache-interest locks that are processed at the DBMS level. The local lock manager of a DBMS, in response to a request for either type of lock, may issue a request to the global lock manager for a system-level lock without disclosing to the global lock manager the type of lock requested of the local lock manager. After receipt of the system level lock, the local lock manager can grant either transaction or cache interest locks locally on a data resource if the combined mode of locally-held locks on that data resource is greater than or equal to the requested mode.

Abstract: A computer database system utilizes a method for performing a right outer join of database tables without sorting the inner table (T.sub.2). The processing of each tuple in the outer table (T.sub.1) includes the preservation in the joint output of all tuples in T.sub.2 which are in its responsibility region. The initialization step of the process preserves in the join output all of the tuples in T.sub.2 which have column set values less than the lowest column set value in T.sub.1, i.e. the first tuple in T.sub.1, since T.sub.1 is sorted or accessed using a sorted index. The responsibility region for tuples in T.sub.1, other than the last tuple, is defined as those tuples which have column set values less than the column set value for the next tuple in T.sub.1 and greater than or equal to the column set value for the current T.sub.1 tuple. The last tuple in T.sub.1 must preserve all of the tuples in T.sub.2 which have not already been preserved in T.sub.2, i.e.

Abstract: A method for controlling coherence of data elements sharable among a plurality of independently-operating CPCs (central processing complexes) in a multi-system complex (called a parallel sysplex) which contains sysplex DASDds (direct access storage devices) and a high-speed SES (shared electronic storage) facility. Sysplex shared data elements are stored in the sysplex DASD under a unique sysplex data element name, which is used for sysplex coherence control. Any CPC may copy any sysplex data element into a local cache buffers (LCB) in the CPC's main storage, where it has an associated sysplex validity bit. The copying CPC executes a sysplex coherence registration command which requests a SES processor to verify that the data element name already exists in the SES cache, and to store the name of the data element in a SES cache entry if found in the SES cache. Importantly, the registration command communicates to SES the CPC location of the validity bit for the LCB containing that data element copy.

Abstract: A method is disclosed for a database system for [off-loading] off-loading, to disk [controller] controller, the extraction of committed [data involving the] data. The system first [picking] picks a Commit.sub.-- LSN value and [insuring] insures all the data modified prior to the Commit.sub.-- LSN value is processed following the DBMS policy of reducing some disk I/Os or not for the modified pages cached in the system. If the policy is not to do disk I/Os for such [pages] pages, then the system places the identifiers of those pages in an ignore list. Otherwise, the system writes those pages to disk and empties the ignore list. [After which] Afterwards, the system forwards the ignore list and the Commit.sub.--LSN along with information regarding the data to be processed to the controller. The controller performs the off-load function by reading from disk every page identified by the system except those in the ignore [list] list, and [determining] determining, for each [page] page, if the page's Page.sub.

Abstract: A high-speed cache is shared by a plurality of independently-operating data systems in a multi-system data sharing complex. Each data system has access both to the high-speed cache and the lower-speed, secondary storage for obtaining and storing data. Management logic and the high-speed cache assures that a block of data obtained form the cache for entry into the secondary storage will be consistent with the version of the block of data in the shared cache with non-blocking serialization allowing access to a changed version in the cache while castout is being performed. Castout classes are provided to facilitate efficient movement from the shared cache to DASD.

Abstract: In transaction processing systems, it is known for resource-updating operations within a transaction to be backed out at the request of an application program following detection of error conditions during processing of the transaction. If the error condition is very likely to recur, it may be undesirable for the operations request to be presented to the application exactly as before. A transaction-oriented data processing system and a method of transaction-oriented data processing are provided in which operation requests or data packets may be marked to be excluded from the effects of application-requested backouts.

Abstract: Disk check bits refer to bit patterns stored in particular bytes of a page which are used to detect errors in writing the page to storage. Every time a page is obtained from storage, changed from the version retained in storage, and written back to storage, the check bit pattern on the changed page is altered to be different from the bit pattern on the storage page. This is because the changed page overwrites the stored page. The invention provides a method for managing the check bits in a multi-DBMS system employing a high-speed shared electronic store as a store-in cache for all pages obtained from disk storage. When a page is first obtained from disk storage by a DBMS and changed, check bit information for the page is maintained in a directory of the storing cache which indicates what the patterns are for the version of the page in the disk storage. All pages which are modified are stored in the store-in cache and are only returned to disk storage from the cache.

Abstract: A method and means for achieving files of modifiable pages in a log based phased commit transaction management system (TMS) in which those pages which have been modified since the last full or incremental backup donot require during the copy operation any modifications to the page itself but merely to a common status page. This is accomplished by management of a pair of global log sequence numbers. Comparison between a first number (ICBU.sub.-- LSN) and each data page LSN as the page is modified permits the common status page to be updated to correctly reflect the changed status. Subsequent modifications to the same page donot require amendment of the status page. The status page indicia are reset as part of the backup procedure and for ascertaining the page copy set for incremental copying. The ICBU LSN assumes one of two values as a function of the copy operation and another value for processing page modifications after the copy operation. A second number (ICRF.sub.

Abstract: Database files containing records include pages called free space inventory pages (FSIPs) describing field space information relating to data pages. In a transaction processing system, the invention provides correct sequences for logging of updates to FSIPs when the updates are required by updates or UNDOs to data records. If, during operation to insert a data record to a data page, the FSIP containing free space information for the page indicates that the page is empty and there are no uncommitted deletes to the page, page I/O is avoided by formatting the page directly in a data buffer pool without reading the page from disk. During a cursor stability-level table scan with data record-level locking, excessive I/O and some record locking are avoided by using space reservation fields on an FSIP to ensure that there is no space reserved on the data page for a later undo of uncommitted data records deletes from the page.

Abstract: A data processing system for the storage of persistent and non-persistent data in a queue, and a method for the storage of data which is required to survive a system failure (persistent data) and data which is not required to survive a system failure (non-persistent data) on a single queue, are disclosed. The method involves receiving persistent and non-persistent data to be stored in a queue, then marking the data in time sequence order, before storing the persistent data in a first set of data pages and the non-persistent data in a second set of data pages. Upon receiving a request for removal of data from the queue, both the first and second sets of pages are checked and the data is removed in time sequence order. A log is preferably created to enable recovery in the event of failure and restart of the queue. When receiving and removing persistent data to be stored in and to be removed from the queue, log entries are made of changes to the persistent data only.

Abstract: In a partitioned database system of the Shared Nothing type, one or more secondary replicas of each partition are maintained by spooling (i.e., asynchronously sending) modified (usually called dirty) pages from the primary replica to the secondary replica(s) rather than by using a synchronous page update or by sending log entries instead of entire pages. A Write-Ahead Log protocol is used so that a dirty page is not forced to non-volatile storage until a log record of the modification is created and written to non-volatile storage. Replica updating does not delay the committing of transactions because replica updating is done asynchronously with respect to transaction processing. Since dirty pages are sent rather than only log entries, disk accesses and processing at the secondary replica(s) arising from the maintaining of the replicas are minimized as well. Only one centrally accessible log is maintained for all replicas of the same partition.

Abstract: A method for detecting partial page writes in pages spanning multiple sectors of a sector organized multiple tracked storage facility in a page oriented, log based transaction management system. During a page write to storage from a buffer, a status bit is embedded at the end of each page sector and a status byte in the last page sector, the status byte is complemented, and each status bit is swapped with a counterpart in the status byte as it is being written out to storage. During a page read in the buffer from storage the status bit values of each page are swapped with their byte counterpart and a partial write detected as a mismatch of the bits in the status byte. Page recovery involves recreating a page from said log upon detection of either a partial sector write or a partial page write by redoing all accessing events on the log between a predetermined point to an end of log including unconditionally redoing of all format page events logged in said interval.