Oracle database data type drivers#

It now also supports a variety of data models for storage.

Oracle was initially designed as a relational DBMS. Relational Key/Value Document / XML Graph Triplestore (RDF) In the case of deadlocks, oracle resolves them by rolling back the statements involved in the deadlock and releasing locks. Also, locks are automatically released when transaction no longer needs them. Never escalation is done to avoid the probability of deadlocks. It never escalates locks, which is done to promote the lock level to a higher level when most of the locks are at a given granularity level to decrease the number of locks. Oracle also allows the lock conversions to maintain the consistencies. Oracle automatically uses the lowest application-level lock to provide less restriction, so more data is available to be accessed by others.

When writer A is writing a row, it blocks the concurrent writer B on the same row.

When in the process of modifying a row, it is locked.

Oracle has two types of locks (shared and exclusive) that provide data consistency, concurrency, and integrity. To prevent the incorrect updates of shared data between the concurrent transactions. Read consistency is achieved by reconstructing the data from the undo statements. Read-only isolation level: Similar to serializable isolation, but data is not permitted to be modified in the transaction. Oracle allows modifying a row if the changes made to it by another transaction are already committed before this transaction started. So any commits to the item by another concurrent transaction say t2 is not reflected in the reread of the item by t1 implying read consistency. Serializable isolation: In this, the transaction views the changes committed before the transaction began and not just before the given query. Even though it provides the read consistency(row, when reread, is the same as before if not committed by other transactions), there is a conflicting write issue when two concurrent transactions try to modify the same item. Read committed: The default isolation level where query executed by transaction sees the data committed before the given query statement and thus avoids reading the commits happening while in the transaction. Oracle can prevent dirty reads, non-repeatable reads, phantom reads as it provides: It maintains data consistency by having a multi-version consistency model and the usage of locks and transactions. Oracle uses serializability for transaction isolation. Oracle employs MVCC for concurrency control.

Oracle database data type drivers#

it supports multiple types of workload (OLTP, data warehouse, operational data store, data hub), it can manage and join together multiple types of data (relational, XML, JSON, spatial, property graph, RDF, text, binary) being stored inside or outside the database, it supports numerous deployment types (single instance, clustered shared everything, sharded shared-nothing, reader-farms, on-premises, public cloud, standard hardware, engineered system), and it can be accessed using multiple APIs (SQL, REST APIs, Simple Oracle Document Access, Property Graph Query Language, JDBC/ODBC drivers for multiple languages). Oracle database, originally a relational DBMS, has evolved into a converged, multi-model DBMS, e.g.