Oracle Flashback Technology provides rapid data recovery solutions, reducing recovery time from hours to minutes. It enables selective undoing of errors at various levels including row, transaction, table, and entire database operations. Core Concepts Undo Segments Undo segments store pre-change dat...
-- table used in the examples desc demo_txn; /* Name Null? Type ----- -------- ------------------- TS TIMESTAMP(6) VAL NOT NULL NUMBER */ 1. Implicit COMMIT on normal SQL*Plus exit insert into demo_txn(ts,val) values(systimestamp,1); exit Reconnect: select * from demo_txn; -- one row committed autom...
Redo Logging Modes Overview Redo logging controls how much information Oracle writes to on line redo log files during data changes. Three principal modes exist: LOGGING: Default mode where all DML and object creation actions generate redo entries. Suitable for most database objects; NOLOGGING is gen...
Prerequisites and Environment Setup To enable SSL access for an Oracle database, you need a functioning server and client environment. In this example: Server: CentOS 7.9 running Oracle Database 11.2.0.4.0 Client: Windows Server 2008 R2 running Oracle Client 11.2.0.3.0 Start by creating wallets and...
In Oracle, the queries SELECT * FROM a, b WHERE a.id = b.id and SELECT * FROM a INNER JOIN b ON a.id = b.id are functionally equivalent. Both produce the same result set by matching rows from tables a and b where the id values are equal. However, they differ in syntax style and clarity. The comma-ba...
In Oracle9i and later, sorting of Chinece text can follow phoneitc, radical, or stroke order instead of binary encoding. This behavior is controlled via the NLS_SORT setting. Available linguistic sorts: SCHINESE_RADICAL_M: Sort by radical first, then stroke count. SCHINESE_STROKE_M: Sort by stroke c...
Analyzing Object Storage and Segments 1. Assessing Table Size and Row Counts To evaluate storage consumption across all schemas, join the data dictionary views regarding tables and segments. The following query calculates size in gigabytes and retrieves row estimates. -- Segment size analysis across...
Data Retrieval Fundamentals Retrieve specific columns from a dataset: SELECT first_name, last_name, email FROM employees; Eliminate duplicate values from results: SELECT DISTINCT department_id FROM employees; Filter records based on conditions: SELECT product_name, unit_price FROM inventory WHERE un...
The ORA-12733 error occurs in Oracle databases when a regular expression exceeds the system's maximum allowed length. This limit is enforced by the REGEXP_LIKE function to prevent memory overflow and performance degradation. To address this issue, consider the following approaches: Reduce Regular Ex...
There are two main approacehs for JDBC to connect to an Oracle database: 1. Using the Thin Driver The Thin driver is implemented entirely in Java and establishes a connection to the Oracle database using TCP/IP via Java Sockets. Thiss makes the Thin driver platform-independent. It does not require t...
