International Business Machines Corporation

Aamer U Sachedina

Matthew Albert Huras

Keriley Kay Romanufa

Xun Xue

Ronen Grosman

James Liam Finnie

Bret Ronald Olszewski

Michael Jeffrey Winer

Kevin R Rose

Andrew David Buckler

Michael Edward Factor

Balakrishna Raghavendra Iyer

Garret Frederick Swart

Robert William Lyle

Timothy Ray Malkemus

Christian Marcelo Garcia-Arellano

David Alan Hepkin

Lin Qiao

Paula Kim Ta-Shma

Roger L Q Zheng

Sunil Jeevananda Kamath

Avishay Traeger

Miroslaw Adam Flasza

Leo Tat Man Lau

Stewart L Palmer

Roger Luo Quan Zheng

Robert T Berks

Lan Pham

Roger L Zheng

Taavi Andrew Burns

Kelly W Schlamb

Nickolay V Tchervenski

Mathew Albert Huras

Technology for applying locks to memory pages. More specifically, a sticky lock is chosen by matching observed usage patterns with predetermined patterns associated with various sticky locks and/or types of stick locks increase database performance by reducing required communications and information transfers.

Increase database performance by reducing required communications and information transfers

According to embodiments of the present invention, one or more computer processors determine that a predetermined workload threshold associated with an invalidated object is not exceeded and transmits an invalidation command associated with the invalidated object to the owner of the invalidated object. The one or more computer processors instruct the modifier of the invalidated object to retain possession of a first lock on the object beyond the transaction. The one or more computer processors determine that a usage pattern associated with the invalidated object matches a predetermined usage pattern for selecting a lock that can be retained beyond an associated transaction and transmits a second lock a requestor. The one or more computer processors instruct the modifier to release possession of the first lock to the owner and transmit a first image of the current version of the invalidated object to the owner for subsequent transmission to the requestor.

A storage appliance system is disclosed which may include at least one application server for locally executing an application, and one or more storage servers in communication with the application server for I/O transmission therebetween. Also disclosed are an application server, a method, and a computer program product.

Storage appliance, application server and method thereof

An ordering of operations in log records includes: performing update operations on a database object by a node; writing log records for the update operations into a local buffer by the node, the log records each including a local virtual timestamp; determining that a log flush to write the log records in the local buffer to a persistent storage is to be performed; in response, sending a request from the node to a log flush sequence server for a log flush sequence number; receiving the log flush sequence number by the node; inserting the log flush sequence number into the log records in the local buffer; and performing the log flush to write the log records in the local buffer to the persistent storage, where the log records written to the persistent storage comprises the local virtual timestamps and the log flush sequence number.

Methods to minimize communication in a cluster database system

A method for logical buffer pool extension identifies a page in a memory for eviction, and analyzes characteristics of the page to form a differentiated page. The characteristics of the page include descriptors that include a workload type, a page weight, a page type, frequency of access and timing of most recent access. The method also identifies a target location for the differentiated page from a set of locations including a fastcache storage and a hard disk storage to form an identified target location. The method further selects an eviction operation from a set of eviction operations using the characteristics of the differentiated page and the identified target location. The differentiated page is written to the identified target location using the selected eviction operation, where the differentiated page is written only to the fastcache storage.

Logical buffer pool extension

Techniques are provided for accessing sector data. An embedded storage function is received. One or more data management functions are generated in response to receiving the embedded storage function. The one or more data management functions are invoked to retrieve the sector data from a sector table.

Implementing storage management functions using a data store system

A system and a method for performing a warm shutdown and restart of a buffer pool. The buffer content, including pages and control structures associated with these pages, is partitioned into blocks, where block is saved to a disk as a sequential file. The size of each block is selected to provide an optimal I/O efficiency during buffer pool shutdown and restart operations. Blocks can be saved simultaneously using a plurality of writer threads. During restart of the buffer pool, the control information is read from the disk and restored to the buffer pool using reader threads. The buffer pool may be made available for reference to pages while the reader threads are enabled to read the saved information by blocks, to facilitate a more rapid restoration of information in the buffer pool.

Method for performing a warm shutdown and restart of a buffer pool

Lock communications in a shared disk database system is reduced by several approaches: sending a single message to a lock manager for locks required for an operation and locks that will be required in the future, the operations may include row update, row delete, large scan, and row insert; performing an operation in two executions, where in a first execution locks required for the operation is determined without performing the operation, and in a second execution a single message is sent to a lock manager for the required locks and the operation is performed; in free space searching, sending a single message to a lock manager for row and page locks before a row insert is actually performed; and granting locks in an unfair manner.

Approaches to reducing lock communications in a shared disk database

A method, computer program product, and system for detecting and fencing off a failed entity instance so that failover time in the computing system is reduced. Upon detection of a failed entity, for example a failed process, a signal handler invokes an operating system interface to fence off the failed instance from modifying its persistent state, so that the entity may be re-instantiated prior to termination of the failed instance. This approach reduces failover time and eliminates split-brain problems without compromising access to the failed instance to obtain diagnostic information, core dumps, and the like.

Failure detection and fencing in a computing system

According to one embodiment of the present invention, a method of detecting and correcting hot pages in a database system includes monitoring transactions involving pages in a database and determining if one of the transactions had to wait for access to one of the pages; incrementing a page contention counter each time one of the transactions had to wait for access to one of the pages. The method then determines if the page contention counter exceeds a predetermined threshold and monitors transactions on one of the pages for which the page contention count was exceeded. The method then determines if a row was accessed in the page for which the page contention count was exceeded and increments a reference count for the accessed row. The accessed rows are flagged when the reference count exceeds a second predetermined threshold. The flagged rows are moved to another page in the database.

Automatic detection and correction of hot pages in a database system

For an information retrieval system coupled to a buffer pool maintaining a plurality of pages of recently accessed information for subsequent re-access, a technique for starting the buffer pool is provided. The technique facilitates a quicker start to the buffer pool by deferring allocation of page storing portions, for example, until they are needed. The technique makes the buffer pool available for storing pages while deferring allocation of a page storing portion of the buffer pool and allocates the page storing portion of the buffer pool in response to a demand to store pages to the buffer pool. The technique may be used to re-start a buffer pool with pages stored to a memory coupled to the information retrieval system where the pages where stored upon a buffer pool shutdown. Further, buffer pool readers or prefetchers may be configured to read pages for storing to the buffer pool and allocate the page storing portions of the buffer pool in response to instructions to read particular pages.

System and method for starting a buffer pool

Provided are a method, system, and program for handling access requests to a page while copying an updated page of data to storage. An update to a page in a memory is received and indication is made that the page has an exclusive lock. The update is applied to the page and an operation is initiated to copy the updated page to a physical log in a storage in response to applying the update to the page. Reads and writes are allowed to proceed against the page while the operation to copy the updated page to the physical log in the storage is occurring.

Handling access requests to a page while copying an updated page of data to storage

A system and method for managing shared resources is disclosed. The system includes a primary coherency processing unit which processes lock requests from a plurality of data processing hosts, the primary coherency processing unit also storing a first current lock state information for the plurality of data processing hosts, the first current lock state information including a plurality of locks held by the plurality of data processing hosts. The system further includes a standby coherency processing unit storing fewer locks than the primary coherency processing unit, the locks stored by the standby coherency processing unit being a subset of locks included in the first current lock state information, the standby coherency unit configured to perform a plurality of activities of the primary coherency processing unit using the subset of locks in response to a failure of the primary coherency processing unit.

Improving data availability during failure detection and recovery processing in a shared resource system

A computer system dynamically scales back latch requests for system resources. Tasks seeking access to system resources each dynamically determine the probability that the task will gain access to the latch relating to a given system resource. Where the task estimates that its probability is below a defined threshold, the task will suspend itself for a defined sleep time. The task dynamically adjusts the length of the sleep time based on the number of times the task enters the suspended state and on the relative changes in the estimated probability that the task will gain access to the resource.

Dynamic latch request scaling back function to conditionally place task in suspended state

A method and system for improving memory access patterns of software systems on NUMA systems discovers NUMA system resources where the NUMA system resources comprises a plurality of NUMA nodes; determines a plurality of database threads, processes, and objects for a database configuration; and generates a policy which assigns the plurality of database threads, processes, and objects to the plurality of NUMA nodes, wherein the generating of the policy is performed prior to initialization of the plurality of database threads, processes, and objects. The assignment of the database threads, processes, or objects to NUMA nodes is such that the amount of remote memory accesses is reduced. When the database thread, process, or object initializes, the database server queries the policy for its assigned NUMA node(s). The database thread, process, or object is then bound to the assigned NUMA node(s).

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Queensville, Canada

Aamer U Sachedina