International Business Machines Corporation

Effi Ofer

Roger L Q Zheng

Dale Murray McInnis

Matthew Albert Huras

Michael Jeffrey Winer

Steven Robert Pearson

Jason Christopher Young

Scott David Lashley

Kevin James Cherkauer

Bruce M Jackson

Yuke Zhuge

Mark Dennehy

Roger Luo Q Zheng

Kirill Bogdanov

Diarmuid Flynn

Marzia Mura

Danny Harnik

Xun Xue

Ety Khaitzin

Ohad Eytan

Dafna Sadeh

A method for managing a data cache, comprising: storing a cache management list comprising a plurality of entries and having: a tail part stored in a first storage and documenting recently accessed data items stored in the data cache, a body part stored in a second storage and documenting less recently accessed data items stored in the data cache, and a head part stored in the first storage and documenting least recently accessed data items stored in the data cache; and in each of a plurality of iterations: receiving at least one data access request; documenting the data access request in the tail; identifying a plurality of duplicated entries present in the body and the tail; and removing each of the plurality of duplicated entries from the body in the second storage according to a physical organization in the second storage of the plurality of duplicated entries.

Managing a least-recently-used data cache with a persistent body

An apparatus, a computer program and a method for prefetching a predetermined number of data items to a cache. The method comprises obtaining a list of candidate data items and associated scores thereof, that comprises more candidate data items than the predetermined number of data items to be prefetched to the cache. The method comprises repeatedly selecting, based on scores of the candidate data items, a candidate data item from the list and determining whether to add the candidate data item to the cache. Determining whether to add the candidate data item to the cache comprises determining whether the candidate data item is retained by the cache; and in response to determining that the candidate data item is not retained by the cache, adding the candidate data item thereto. The repeatedly selecting and determining are performed until the predetermined number of data items is added to the cache.

Method and apparatus for prefetching data items to a cache

Data integrity is maintained during failed communications between a member node of a primary cluster and a backup cluster by assigning an assisting member node to run an assisting process that transmits data entered into the member node to the backup cluster. In this way, a replicated database is maintained during a partial communication failure between the primary cluster and the backup cluster.

Handling failed cluster members when replicating a database between clusters

A log-shipping data replication system employs a primary server coupled to a standby server. In operation, the primary server concurrently flushes log data at the primary server and transmits the same log data from the primary server to the standby server. The primary server further transmits at least one buffer flush boundary indication to the standby server indicating the flushing status of the log data at the primary server. The standby server processes the log data as a function of receiving the log data from the primary server, and/or receiving the at least one buffer flush boundary indication from the primary server.

Log shipping data replication with parallel log writing and log shipping at the primary site

A method and system are provided for providing a consistent reintegration of a failed primary instance as a new secondary instance with implementation of truncation of log records. Upon failure of a primary instance, a secondary instance may be reassigned as the new primary instance. Prior to reintegration, any portion of the database log of the failed primary that is after the log position of the new primary instance may be truncated, followed by a comparison of the log positions of both the new primary instance and the new secondary instance. In limited circumstances, the truncation of the log data generated by the failed primary instance after the point of failure is possible, and supports reintegration of the failed primary as a new secondary instance with limited overhead.

Consistent reintegration of a failed primary instance

A technique for recovering a dropped table is provided. One or more table spaces are specified prior to one or more tables being dropped from the specified one or more table spaces. When a table is to be dropped from the one or more specified table spaces, a table identifier, a time stamp, and table definition attributes are stored for the dropped table in a data structure and the table is dropped. Upon receiving a request to restore a table space from the one or more specified table spaces, each of the one or more tables in the table space being restored is recovered using the data structure.

Method, system, computer product for recovering dropped database table specifying one or more table spaces, recovering the table space being restored using the dropped table history data structure

A database management system having a dropped table recovery flag. If the dropped table recovery flag is on at the time that a table is dropped, an entry will be made in a dropped table history file. The dropped table history file contains a timestamp of the time of table drop, a unique dropped table identifier, and table definition information. The system includes a command to permit the table-space of a dropped table to be restored and rolled forward to the point of the dropped table drop. The restored and rolled forward dropped table data is written to a flat file. The flat file data is loaded into a recreated table in the current table space to recover the dropped table.

Dropped database table recovery

Growing community of inventors

Ramat Gan, Israel

Effi Ofer