This guide explains how to rescue both physically and logically deleted Oracle databases, covering RMAN file recovery, full database restoration, flashback table techniques, recycle‑bin usage, flashback database configuration, and essential backup strategies to prevent data loss.
This article analyzes a slow NOT IN subquery that OceanBase rewrites into a NESTED‑LOOP ANTI JOIN, explains why HASH ANTI JOIN is not chosen due to NULL‑sensitive semantics and missing NOT NULL constraints, compares the behavior with Oracle's Null‑Aware Anti Join, and provides practical rewrite and hint‑based optimization recommendations.
Oracle warns Java developers that upgrading Apple Silicon macOS Sonoma to version 14.4 can crash JetBrains IDEs by sending a SIGKILL signal, and advises postponing the update until a fix is available, highlighting the impact on multiple JDK versions.
The article examines how shifting industry trends, cloud adoption, and the rise of domestic databases force Oracle DBAs to choose between staying the course, expanding their skill set, or pivoting entirely, offering practical guidance for each path.
The article examines Oracle’s evolution from RAC‑based sharding to the 23c Global Distributed Database, highlighting its RAFT replication, cross‑region capabilities, compliance benefits, and performance advantages that position it as a true multi‑cloud, multi‑location solution for modern OLTP workloads.
This article explains the differences between global and local indexes in OceanBase, analyzes why queries using global unique indexes run significantly faster than those using local indexes during Oracle migration, and provides detailed SQL examples, execution plans, and performance testing results to guide database optimization.
This comprehensive tutorial walks you through configuring Oracle Data Guard for master‑slave replication, covering prerequisites, detailed command‑by‑command steps, common pitfalls, testing procedures, switchover operations, and post‑switch recovery, all illustrated with diagrams and code snippets.
This article explains how to locate, trace, and resolve a syntax error that occurs when a stored procedure migrated from Oracle to OceanBase fails, detailing the use of trace IDs, SQL reconstruction, cursor analysis, and the necessary adjustments to primary‑key handling.
This guide provides complete shell scripts and step‑by‑step instructions for performing remote backups and restores of MySQL, Oracle, and PostgreSQL databases on Linux, including directory creation, compression, secure copy, cron scheduling, and cleanup of old backup files.
A veteran Oracle DBA recounts the painful history of early Oracle versions, explains classic errors like ORA-1591 and ORA-1578, shares troubleshooting tactics, and reflects on how those hardships forged the expertise needed to master today’s complex database environments.
The article explains MySQL’s new versioning model, introducing Innovation and Long‑Term Support (LTS) releases, detailing transition timelines, feature deprecation, upgrade and downgrade strategies, and the role of MySQL HeatWave, while also providing links to download and community resources.
This article examines why MySQL permits creating multiple identical indexes on the same column, demonstrates the behavior through several tests, compares it with Oracle's stricter restrictions, and explains how the optimizer selects indexes, highlighting practical implications for database design.
The 2023 State of Java report, based on a survey of over 2,000 Java professionals, reveals that Java adoption stays strong with most companies using LTS versions, migrating to the cloud, confronting rising costs and security challenges, while Oracle's market share declines in favor of OpenJDK alternatives.
This guide details essential Oracle database daily inspection commands—covering instance status, tablespace health, resource usage, performance metrics, server CPU/memory/I/O checks, and security audits—to help DBAs ensure system stability and quickly diagnose issues.
This article investigates why Oracle and OceanBase return different results when querying the USER_TAB_COLUMNS view in stored procedures, demonstrates reproducible tests, analyzes system view behavior, and proposes workarounds such as using ALL_TAB_COLUMNS, creating synonyms, intermediate tables, or materialized views to ensure consistent table name retrieval.
This article demonstrates two practical approaches for handling MySQL auto‑increment columns during migration to OB Oracle—creating custom sequences with DBCAT and using the GENERATED BY DEFAULT AS IDENTITY attribute—provides step‑by‑step commands, scripts, and validation results to help DBA engineers achieve seamless primary‑key migration.
Oracle 23c turns the converged database vision into reality by unifying relational, document, and graph data under a single SQL engine, offering built‑in microservice support, lock‑free reservations, immutable tables, and an integrated SQL firewall to reduce architecture complexity and development cost.
This guide walks through setting up a Spring Boot 2.4.12 project with JDK 1.8, Oracle, and two data sources—master and slave—covering Maven dependencies, application.yml settings, custom property classes, HikariDataSource beans, JPA EntityManagerFactory, MyBatis SqlSessionFactory, mapper scanning, and testing entity creation to verify successful configuration.
This article explains how to improve Oracle database performance by creating archive tables and triggers, and demonstrates step‑by‑step PHP code for connecting to Oracle, moving old records, and querying archived data.
Oracle’s aggressive shift to a per‑employee Java SE subscription has sparked widespread concern among enterprises, as the new pricing tiers and licensing audits threaten to dramatically increase costs and force companies to reconsider their Java deployment strategies.
Oracle's recent shift to a subscription-based Java SE licensing model, featuring employee‑count pricing tiers and aggressive email outreach, has sparked widespread concern among enterprises, prompting costly compliance challenges, discussions of alternative OpenJDK adoption, and calls for careful negotiation with Oracle.
This article explains how to proactively identify non‑conforming date values during Oracle or MySQL data migrations by creating test tables, leveraging DBMS_ERRLOG for Oracle, using strict SQL_MODE and temporary tables for MySQL, and optionally applying regular‑expression checks.
This article explains why AUTO_INCREMENT is unsupported in OceanBase Oracle tenants, introduces four practical ways to implement auto‑increment columns using sequences, DML, DDL, triggers, and the GENERATED BY DEFAULT AS IDENTITY syntax, and provides step‑by‑step SQL examples for each method.
This article details a November 2022 database outage caused by a sudden CPU and load surge, explains how the team diagnosed the issue, outlines the emergency steps taken, and shares practical SQL performance optimization recommendations to prevent similar incidents.
The SQLE 2.2305.0-pre3 release introduces Webhook-based work‑order status notifications, Oracle rollback statement generation for the enterprise edition, updated documentation links, a detailed feature list, bug fixes, and references to previous versions and further reading resources.
This article explains how the default PL/SQL delimiter '/' in OceanBase Oracle tenants conflicts with division operators, causing syntax errors, and demonstrates fixing the issue by changing the delimiter to '//' with detailed code examples and execution results.
When a mistaken UPDATE statement overwrites an entire Oracle table, this guide explains four practical recovery techniques—including transaction rollback, flashback queries, LogMiner undo extraction, and RMAN backup restoration—detailing their prerequisites, commands, and trade‑offs.
The article explains how Oracle's built‑in auto‑task jobs run during specific weekday and weekend windows, why they can cause performance degradation by changing execution plans or consuming resources, and provides practical steps to diagnose, adjust windows, and selectively disable problematic tasks.
This article explains why SQL join execution plans often cause severe performance drops after moving from Oracle to domestic or open‑source databases, demonstrates each join type with PostgreSQL examples, shows how plan choices like HASH JOIN versus NESTED LOOP affect speed, and offers rewrite techniques such as NOT EXISTS or UNION to restore efficiency.
This article explains Oracle database backup and recovery fundamentals, classifies failure types, compares logical and physical backup methods, introduces flashback technology, outlines complete and incomplete recovery, and provides practical RMAN scripts and scheduling tips for reliable data protection.
This guide walks you through Oracle's storage architecture, explains when and why to use partitioned tables, details each partition type, and provides step‑by‑step SQL examples for creating, managing, and modifying range, list, hash, and composite partitions.
Oracle’s shift to an employee‑based pricing model for Java SE replaces the old per‑user or per‑processor subscription, potentially raising enterprise Java licensing fees by up to ten times, prompting concerns of predatory pricing and forcing companies to reassess their Java cost structures.
Oracle’s newly released Java SE Universal Subscription price list introduces tiered per‑employee fees that can dramatically increase costs for companies with large staff but few Java users, while offering unchanged terms for existing subscribers and no impact for OpenJDK users.
This article explains how to retrieve data from an Oracle database with cx_Oracle, convert it to a pandas DataFrame, and correctly write the results to an Excel file with column headers, providing a complete code example and a practical solution to a common data‑processing issue.
This guide explains how to create a custom Oracle datasource plugin for Nacos 2.2 by adding Maven dependencies, importing the Oracle SQL script, configuring connection properties, and setting the datasource platform, enabling Nacos to use Oracle instead of the default MySQL or Derby.
Oracle’s Enterprise Performance Pack, offered free to Java SE subscribers and OCI users, brings Java 17‑level memory management and performance enhancements—including modern garbage collection, compact strings, and improved observability—to legacy Java 8 applications, delivering up to 40% better memory and CPU efficiency under heavy loads.
A comprehensive TPC‑H benchmark compares ClickHouse, Oracle, and the open‑source esProc SPL across simple and complex queries, showing ClickHouse excels at single‑table scans, while SPL consistently outperforms both in complex calculations and offers more concise code.
This article traces the history of the JavaScript trademark—from its creation by Netscape and Sun, through Oracle’s acquisition, to Ryan Dahl’s 2022 open letter urging its release, highlighting the confusion with Java and the rise of ECMAScript as a neutral name.
The September 2023 DB-Engines ranking update shows Oracle’s steep decline, while MySQL and MongoDB gain points, and presents the top ten databases across relational, key‑value, document, time‑series, and graph categories along with the five metrics used to calculate popularity.
The September DB‑Engines ranking shows Oracle’s steep decline while MySQL and MongoDB climb, presents top‑10 lists for relational, key‑value, document, time‑series and graph databases, explains the five metrics behind the scores, and advises professionals to choose databases based on business needs rather than pure popularity.
This article benchmarks ClickHouse, Oracle, and the open‑source esProc SPL on the TPC‑H suite, showing ClickHouse excels at simple scans, Oracle handles many complex queries, while SPL consistently outperforms both in speed and code simplicity across a range of workloads.
The article examines the growing demand for HTAP databases, comparing cloud‑native solutions such as Google AlloyDB, Oracle MySQL HeatWave, Amazon Aurora, and domestic offerings like TiDB and OceanBase, analyzing their architectures, offload mechanisms, performance claims, and trade‑offs for mixed OLTP/OLAP workloads.
The August 2023 DB‑Engines ranking shows Oracle’s steep 19.5‑point drop, while MySQL and MongoDB surge, PostgreSQL continues rising, and the top‑10 list highlights shifts across relational, key‑value, and document databases, with methodology based on search, job, and community metrics.
Java SE 7 will lose extended support in July 2022, moving to sustaining support with no patches or security fixes, while Oracle recommends upgrading to supported long‑term versions like Java 8, 11, or 17 to stay secure and up‑to‑date.
The July 2023 DB-Engines ranking shows Oracle, PostgreSQL and MongoDB slipping, while MySQL and Microsoft SQL Server climb, and provides detailed scores, trend charts, and the methodology behind the monthly popularity scores for the top ten database systems.
The article examines how to design cross‑database date and time storage by comparing MySQL, Oracle, and SQL Server date‑time types, discussing their formats, ranges, storage sizes, and trade‑offs, and proposes practical solutions such as using timestamps, custom conversion functions, and ORM considerations.
This guide shows how to use Python and pandas to prepare datetime data, then insert it in bulk into Oracle and MySQL databases, handling type conversions with Oracle's TO_DATE and MySQL's STR_TO_DATE functions while managing transactions safely.
This article shares practical experiences and lessons learned from over a hundred database migration projects, comparing storage replication, logical replication, and ASM disk‑group rebalancing, and explains how system context, vendor capabilities, and careful planning determine the most suitable approach.
This article explains how to use Oracle Data Pump's ESTIMATE and ESTIMATE_ONLY parameters to assess the size of a 1 TB production database for migration, compares BLOCKS and STATISTICS estimation methods, and details best practices for gathering accurate optimizer statistics with ANALYZE and DBMS_STATS.
The article explains why Oracle can release MySQL under a dual GPLv2/commercial licensing model, how the GPL works, the impossibility of changing licenses for existing versions, and proposes creating a domestically controlled GPL‑v2 MySQL fork to avoid future licensing risks.
The May 2023 DB-Engines ranking shows Oracle gaining the most points while MySQL and SQL Server plunge, and PostgreSQL and Redis surge dramatically, with detailed score changes, top‑10 lists across database categories, and the methodology behind the popularity metrics.
This article provides a comprehensive overview of Oracle's database products, explaining why they matter, detailing the physical and logical storage structures, instance processes and memory areas, and tracing the evolution from early versions through RAC, multitenancy, and the latest 18c features.
This article provides a thorough guide to SQL fundamentals—including SELECT, FROM, WHERE, GROUP BY, HAVING, ORDER BY, LIMIT, aggregate functions, joins, set operations, and Oracle-specific objects—followed by a collection of common interview questions with detailed solutions, top‑N queries, and row‑to‑column transformations, while also containing promotional notes for related resources.
The article examines Oracle’s automatic predicate pushdown that rewrites SQL statements, illustrates its impact on execution plans with trace data and queries, and draws lessons for improving domestic database products and support in the wake of recent geopolitical shifts.
Oracle has begun auditing Java usage across enterprises, introducing paid licensing models for Java SE, offering a limited free tier for Java 17, and prompting many companies to switch to OpenJDK to avoid compliance penalties and costly subscriptions.
Oracle has begun formally auditing Java usage, extending its software‑license checks to the Java platform and demanding subscriptions for even older versions, a move that could force enterprises to pay hefty fees for compliance.
The article analyzes how comprehensive Western sanctions against Russia are prompting China to accelerate self‑reliance in foundational software, examines Oracle's pivotal role in Chinese enterprises, and discusses the strategic, technical, and market obstacles to achieving a successful "de‑IOE" transition.
The article provides a comprehensive overview of Oracle Real Application Cluster (RAC), detailing its two‑part architecture of Clusterware and RAC instances, shared storage configurations, key Clusterware processes, storage options, benefits such as load balancing and high availability, as well as its management and planning considerations.
This article details the common pitfalls encountered when synchronizing Oracle databases to AnalyticDB PostgreSQL, covering null versus empty string handling, data type conversion challenges, character set issues, special character processing, and comprehensive testing strategies to ensure data consistency and performance.
The article examines Oracle’s unexpected predicate‑pushdown rewrite observed in trace files, shows how it alters execution plans through a virtual column index, and draws lessons for Chinese database vendors on product depth, architecture design, and after‑sales support to close the gap with global leaders.
Oracle’s Solaris CBE, introduced after the 2009 Sun acquisition, provides a pre‑release OS version that often lags behind the monthly SRU updates, leaving developers without the latest free‑license features despite Oracle’s commitment to support Solaris through 2034.
This article provides a step‑by‑step guide on configuring DTLE 4.22.01.0 to perform Oracle‑to‑MySQL incremental data synchronization, covering type mapping, DML/DDL support, environment setup, job creation, data verification, and handling of compatibility limitations.
This article explains how a deep understanding of database internals, illustrated by an Oracle recovery story, enables you to restore PostgreSQL instances when WAL files or pg_control are missing, providing detailed command parameters, preparation steps, and cautions for safe recovery.
The SQLE 1.2202.0 release introduces new user group and permission management, scoring for audit results, expanded support for MySQL, Oracle, Java application SQL capture, Db2 audit plugins, additional MySQL audit rules, UI optimizations, and several critical bug fixes.
The SQLE 1.2202.0-pre1 release introduces a preview version of the open‑source SQL audit platform with new user‑group permissions, task scoring, support for MySQL schema audits, Oracle TopSQL capture, and Java application SQL capture, along with links to the repository, documentation, and plugin development guide.
This article presents four real‑world Oracle SQL cases—from a Cartesian join that halted nightly reports to a varchar primary key causing full scans, non‑standard date syntax breaking partition pruning, and missing statistics leading to unstable plans—detailing analysis, execution‑plan insights, and concrete remediation steps.
The article explains the purpose, history, member composition, activities, and selection process of the Java Champions program, highlighting its prestige within the Java ecosystem and noting the limited number of Chinese members and available public resources.
A former Oracle MySQL lead engineer denounces MySQL as a poor open‑source database, praises PostgreSQL, critiques MariaDB, and discusses the historical evolution and corporate politics behind these relational database systems.
This article walks through the complete process of moving an Oracle database to PostgreSQL, covering the rationale for open‑source and cloud solutions, the three core migration phases, hands‑on demos of AWS SCT, Ora2PG, and a Python‑based data‑replication example, plus performance results.
The SQLE 1.2111.0 release introduces online DDL support, LDAP login, custom database extensions, PostgreSQL and Oracle audit plugins, several UI optimizations, and a long list of bug fixes addressing rollback generation, configuration password changes, CI triggers, and plugin rule execution.
This tutorial walks beginners through the fundamentals of SQL, explaining what it is, how to run simple SELECT statements, create tables, insert, update, delete records, use WHERE clauses, and even generate fun graphics like stars and calendars using advanced queries.
Learn how to extend Nacos’s configuration persistence beyond Derby and MySQL by cloning the feature_multiple_datasource_support branch, compiling the source with Maven, configuring Oracle as a datasource in application.properties, and launching Nacos in standalone mode, with step‑by‑step commands and essential scripts.
This article investigates the Alibaba Java Development Manual’s rule against joining more than three tables by designing and running large‑scale MySQL and Oracle experiments, analyzing performance impacts, presenting test results with and without indexes, and providing full DDL/DML scripts for reproducing the tests.
This article examines how Oracle, PostgreSQL, and MySQL implement and use database sequences for primary keys, covering explicit calls, trigger‑based, DEFAULT, and AUTO_INCREMENT methods, version support, and the effects of INSERT, UPDATE, DELETE, and TRUNCATE operations, concluding with a comparative summary.
This article introduces the 'DBA攻坚指南' book, detailing its Oracle and MySQL performance‑tuning content, author credentials, key chapters, SQL health‑check scripts, usage examples, and the accompanying giveaway event organized by the 爱可生开源社区.
This article examines a real‑world Oracle SQL query, identifies costly full‑table scans and low‑selectivity columns, and demonstrates how creating an index on a key column reduces execution time from 24 minutes to just one second, highlighting essential SQL performance‑tuning techniques.
This guide walks through restoring a mistakenly updated Oracle 11.2.0.1 table to a specific point in time using RMAN tablespace recovery on a new host, handling Windows-specific issues, and finally retrieving the data via a database link, with full scripts and step‑by‑step instructions.
This guide explains how to create an Oracle table with a BLOB column, insert binary files from Python using cx_Oracle by binding a BLOB variable, and later read the stored BLOB back to a file, covering all required SQL and Python code.
Learn ten practical strategies—from safe change rollbacks and cautious destructive commands to robust backups, clear prompts, vigilant monitoring, and disciplined handovers—that help DBAs and operations engineers avoid costly system failures and maintain reliable production environments.
This comprehensive tutorial walks through preparing the environment, configuring yum repositories and hosts, installing Oracle Grid Infrastructure with ASM disk groups, creating ASM disks, and finally building an Oracle database on a CentOS 7 system, including command examples and GUI steps.
This guide walks through setting up a Spring Boot 2.1.4 application with JDK 1.8, Oracle, and HikariCP to use separate master and slave data sources, covering Maven dependencies, YAML configuration, custom property classes, JPA EntityManager factories, MyBatis SqlSession factories, mapper scanning, and sample entity definitions.
This guide walks through configuring ShardingSphere with Oracle in a Spring Boot‑MyBatis‑JPA project, shows custom sharding algorithms, entity/DAO/service code, and details the step‑by‑step debugging that uncovered schema handling bugs and version‑specific quirks, ending with a working solution.
This article walks through using ADDM to pinpoint problematic SQL statements in Oracle, creating and executing a SQL Tuning Advisor task, evaluating profile and index recommendations, and applying parallel execution to dramatically improve performance and resource usage.
This comprehensive tutorial walks you through preparing the environment, configuring the OS, setting up ASM disk groups, installing Oracle Grid Infrastructure, creating ASM disks, and building a database on a CentOS 7 cluster, complete with detailed screenshots for each step.
The article investigates the Alibaba Java development guideline that forbids joining more than three tables by designing MySQL and Oracle experiments, generating massive test data, measuring query performance, analyzing index usage, and concluding why the rule exists and when it can be relaxed.
The article traces database technology from the commercial Oracle era through open‑source and the emerging cloud‑native phase, highlights cloud as the primary battleground and the importance of the to‑B market, reviews historic academic contributions, examines Oracle and China’s TDSQL evolution, and outlines five future directions—distributed, intelligent, multi‑model, hardware‑software integration, and cloud convergence—while urging DBAs to adapt their full‑stack skills.
This article walks through three data‑sync strategies for Elasticsearch, then details a complete Logstash JDBC configuration to pull Oracle records into an ES index, including setup, parameter explanations, startup commands, and verification via Kibana.
This comprehensive guide covers fundamental SQL clauses, aggregate functions, joins, set operators, Oracle-specific objects, essential DML/DDL commands, and a curated collection of 50 interview questions with detailed query examples and performance tips for database professionals.
This comprehensive guide explains how to migrate Oracle databases to MySQL by detailing type differences, migration steps, performance tuning, and validation techniques, while highlighting common pitfalls such as data‑type mismatches, character‑set issues, LOB handling, and transaction isolation nuances.
This article explains common reasons why Oracle indexes may be ignored—such as column comparisons, NULL values, NOT conditions, wildcard placement, functions, data type conversions, arithmetic predicates, and special index types—and provides practical SQL examples and tips to ensure indexes are utilized for better query performance.
This article explains various situations—such as column-to-column comparisons, NULL values, NOT conditions, wildcard LIKE patterns, functions on indexed columns, low‑cardinality leading columns in composite indexes, implicit datatype conversions, arithmetic predicates, virtual and invisible indexes—that can cause an otherwise usable index to be bypassed by the optimizer, leading to full‑table scans.
The Supreme Court ruled APIs uncopyrightable, letting Google use Java code in Android, while LG exits the smartphone market, a massive Facebook data leak surfaces, UK developer jobs surge amid skill shortages, and Python 3.9.4 patches critical security flaws.
The DB-Engines April 2021 popularity ranking shows the top ten databases unchanged, major score drops for Oracle, MySQL and SQL Server, steady gains for PostgreSQL and MongoDB, and rapid climbs for Snowflake and ClickHouse, with methodology based on five key popularity indicators.
This article compiles the most frequently asked questions about OpenJDK, covering Oracle's open‑source strategy, licensing details, compatibility testing, contribution guidelines, and the relationship between OpenJDK and Oracle JDK, providing clear answers for developers and organizations.
This article details how a bank transformed its retail system data pipeline from a monolithic DB2 setup to a distributed Oracle‑Hadoop architecture, evaluated five extraction tools, selected Sqoop direct mode, and implemented customizations to achieve over 50% performance gains and reliable incremental data capture.
This article explains the characteristics of OLTP and OLAP workloads, compares their I/O patterns, and provides Oracle database performance best‑practice guidelines, including storage planning, SAN architecture, operating‑system queue‑depth settings, and SwingBench testing results for optimal configuration.
This guide walks through setting up an Oracle‑MySQL transparent ODBC gateway on RHEL, covering driver installation, odbc.ini and listener configuration, DBLINK creation, a common WHERE‑clause loss problem, and the solution of switching to the ANSI ODBC driver.
This article investigates why the Alibaba Java Development Manual advises against joining more than three tables by designing and executing large‑scale MySQL and Oracle experiments, analyzing query performance, indexing effects, and data‑generation scripts to determine the practical limits of multi‑table joins.
The article investigates the Alibaba Java Development Manual's rule against joining more than three tables by designing and executing extensive MySQL and Oracle experiments, generating massive test data, measuring query performance, and concluding that the restriction stems from join scalability limits on large datasets.
During a morning peak on December 15, 2020, a customer's Oracle RAC cluster hit 100% CPU on both nodes, causing severe response delays, and after detailed session analysis and SQL rewrite the CPU load dropped dramatically, restoring normal service performance.
