International Business Machines Corporation

Dung Kim Nguyen

Juan Li

Hai-Fang Yun

Mayank Pradhan

Steven D Gerdt

Kevin F Smith

Aare Onton

Mien Shih

Michael Reese Jones

M Jaishankar Menon

A system and computer-based method is provided for context-sensitive decomposition of a markup based document into a relational database, based on schemas with reusable item declarations. The user creates a mapping document from a schema of a markup based document with at least one reusable item declaration defining an item being mapped to different tables/columns pairs, depending on the item's ancestry. Mapping document is then annotated with the item ancestry mapping annotation having a location path of the item. Each item is decomposed into a corresponding table column. Preferably, the mapping document is an annotated XML Schema.

System and method for context-sensitive decomposition of XML documents based on schemas with reusable element/attribute declarations

Methods for pre-processing mapping information for efficient decomposition of an XML document for storage in a database are provided. The method includes receiving a mapping document that describes how all of (or a portion of) an XML document is to be decomposed, transforming the mapping document into a data structure for decomposing an XML document, and making the data persistent for use with a subsequent decomposition operation that decomposes an XML document.

Method for pre-processing mapping information for efficient decomposition of XML documents

A system and computer-based method is provided for decomposing and storing a markup based document into a relational database. For a schema of a markup based document a user identifies multiple items mapping into a same database table-column pair, creates a logical table and associates the logical table to each item and a corresponding database table. Next, a user creates a mapping document of the markup based document with mapping annotations defining mapping of the items into columns of the logical tables. Decomposition of each item into a corresponding logical table column is accomplished by collecting the item content from the markup based document and storing it in the corresponding row column.

System and method for decomposition of multiple items into the same table-column pair without dedicated mapping constructs

Aspects for handling destage requests during shutdown in a log-structured array storage subsystem are described. In a method aspect, the method includes receiving a shut-down command, and utilizing at least three data structures for tracking destage requests when the shut-down command is received, wherein closing of open segments before completion of the shut-down is ensured. A further method aspect includes maintaining an outstanding requests list and destage requests list, forming a missing requests list based on the contents of the outstanding requests list and destage requests list when a shut-down command occurs, and tracking destage request processing with the outstanding requests list, destage requests list and missing requests list until all destage requests have been successfully completed.

Method and system for handling destage requests during shut-down in a log-structured array

In a storage system comprising an array of storage devices, including a processor and memory, a plurality of logical tracks are organized on the storage devices in segments comprising columns striped across the storage devices. A system and method are provided for storing logical tracks in the storage devices. Sequentially logically related logical tracks are stored together in neighborhoods. Logical tracks of the same neighborhood destaged at the same time are assigned to a single open segment with other logical tracks of the same neighborhood type. The time at which open segments are designated as closed segments to be written to the storage devices is based on performance, disk utilization and memory utilization criteria. Logical tracks are never split between segment columns. Also, attempts are made not to split a neighborhood of logical tracks being destaged together between segment columns.

System and method for organizing data stored in a log structured array

Aspects for increasing concurrency during staging and destaging of a log structured array (LSA) are described. In an exemplary method aspect, the method includes determining a process type making a request for access to a locking mechanism associated with an LSA directory entry for a logical track, and determining a lock status for the locking mechanism. Access to the locking mechanism is then provided according to the determined process type and lock status. Further, a destaging process is allowed to obtain an available locking mechanism in a read-write mode, a staging process is allowed to obtain an available locking mechanism in a read-only mode, and a garbage collection process is allowed to obtain an available locking mechanism initially in a read-only mode and subsequently in a read-write mode, wherein increased concurrency results during the staging and destaging processes.

Method and system for increasing concurrency during staging and destaging in a log structured array

In a storage system comprising an array of storage devices, including a processor and memory, a plurality of logical tracks are organized on the storage devices in segments comprising columns striped across the storage devices. A system and method are provided for storing logical tracks in the storage devices. Sequentially logically related logical tracks are stored together in neighborhoods. Logical tracks of the same neighborhood A0 destaged at the same time are assigned to a single open segment with other logical tracks of the same neighborhood type. The time at which open segments are designated as closed segments to be written to the storage devices is based on performance, disk utilization and memory utilization criteria. Logical tracks are never split between segment columns. Also, attempts are made not to split a neighborhood of logical tracks being destaged together between segment columns.

In a storage system comprising an array of storage devices including a processor and memory, a plurality of data blocks are organized on the storage devices in segments striped across the storage devices. A main directory, stored in memory, contains the location on the storage device of each of the data blocks. For each segment a segment directory having information on the data blocks in the segment is stored on the storage devices. When a damaged segment directory is detected, a checkpoint of the main directory is written to the storage devices. A list is maintained of damaged segment directories such that segments on the damaged segment directories list are not garbage collected. Following a main directory recovery procedure, the damaged segment directories are reconstructed using the main directory.

System and method for recovering a segment directory for a log

In a storage system comprising an array of storage devices including a processor and memory, a plurality of data blocks are organized on the storage devices in segments striped across the storage devices. A main directory stored in memory contains the location on the storage device of each of the current data blocks. A method is provided for recovering a main directory in the event that the main directory becomes damaged. A segment directory having information on the data blocks in the segment is stored as part of the segment on the storage devices. Periodically a checkpoint of the main directory is written to the storage devices. A list is maintained of closed segments written to the storage devices since the checkpoint directory was written to the storage devices. During a main directory recovery procedure, the checkpoint of the main directory is read into memory, and for each segment that is indicated by the closed segments list as having been closed since the checkpoint of the main directory was written to the disk, the information in the corresponding segment directory is used to update the checkpoint directory.

System and method for recovering a directory for a log structured array

A method for rebuilding contents of a malfunctioned direct access storage device within a log-structured array is disclosed. In accordance with the method and system of the present invention, each direct access storage device within a log-structured array is divided into multiple segment-columns, and each corresponding segment-column from each direct access storage device within the log-structured array forms a segment. A segment is first located within the direct access storage devices. A determination is made as to whether or not the segment is empty. In response to a determination that the segment is empty, a pointer is moved within a segment-column mapping table from pointing to a segment-column in the malfunctioned direct access storage device to point to a segment-column in a spare direct access storage device of the segment. In response to a determination that the segment is not empty, rebuilding contents of the segment-column in the malfunctioned direct access storage device to the segment-column in the spare direct access storage device, and moving the pointer within the segment-column mapping table from pointing to the segment-column in the malfunctioned direct access storage device to point to the segment-column in the spare direct access storage device of the segment. The process then returns to the determination step until all segment-columns within the malfunctioned direct access storage device are rebuilt.

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San Jose, CA, United States of America

Dung Kim Nguyen