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Full ACID transaction management systems are provided by some ISAM client–server implementations. [5] These are the basic concepts behind a database management system (DBMS), which is a client layer over the underlying data store. ISAM was replaced at IBM with a methodology called VSAM (virtual storage access method).
Database tuning describes a group of activities used to optimize and homogenize the performance of a database. It usually overlaps with query tuning, but refers to design of the database files, selection of the database management system (DBMS) application, and configuration of the database's environment ( operating system , CPU , etc.).
Database systems usually implicitly create an index on a set of columns declared PRIMARY KEY, and some are capable of using an already-existing index to police this constraint. Many database systems require that both referencing and referenced sets of columns in a FOREIGN KEY constraint are indexed, thus improving performance of inserts ...
By contrast, column-oriented DBMS store all data from a given column together in order to more quickly serve data warehouse-style queries. Correlation databases are similar to row-based databases, but apply a layer of indirection to map multiple instances of the same value to the same numerical identifier.
Load testing is the simplest form of performance testing. A load test is usually conducted to understand the behavior of the system under a specific expected load. This load can be the expected concurrent number of users on the application performing a specific number of transactions within the set duration.
The OS 2200 database managers are all part of the Universal Data System (UDS). UDS provides a common control structure for multiple different data models. Flat files (sequential, multi-keyed indexed sequential, MSAM, and fixed-block), [1] network, [2] and relational [3] data models all share a common locking, recovery, and clustering mechanism.
The IBM Information Management System (IMS) is a joint hierarchical database and information management system that supports transaction processing. [1] Development began in 1966 to keep track of the bill of materials for the Saturn V rocket of the Apollo program, and the first version on the IBM System/360 Model 65 was completed in 1967 as ICS/DL/I and officially installed in August 1968.
The changes are first recorded in the log, which must be written to stable storage, before the changes are written to the database. [2] The main functionality of a write-ahead log can be summarized as: [3] Allow the page cache to buffer updates to disk-resident pages while ensuring durability semantics in the larger context of a database system.