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Home

Technical Articles

Database

Oracle

How does Oracle support JSON data types and operations?

OraclesupportsJSONdatatypesandoperationssinceOracle12c,enablingefficientstorage,querying,andmanipulationofsemi-structureddatawithinarelationalSQLenvironment.1.JSONdataisstoredusingVARCHAR2,CLOB,orBLOBtypeswithacheckconstraint(ISJSON)toensurevalidity.

Jul 21, 2025 am 03:42 AM

How can you troubleshoot Oracle Net Services connection issues (e.g., using tnsping, sqlplus)?

The method to solve the Oracle database connection error "TNS: could notresolvetheconnectidentifier" or "ORA-12154" is as follows: 1. Use tnsping to check the TNS alias to ensure that the tnsnames.ora file is correct and syntax is correct, and use the full path to execute tnsping when necessary; 2. Use sqlplus to try the actual connection to troubleshoot authentication problems, listener status and version compatibility; 3. Check network and environment variables to confirm that the ping can be reached by the database server, the telnet port is accessible, and there is no firewall blocking, and verify that the ORACLE_HOME and TNS_ADMIN settings are correct.

Jul 21, 2025 am 03:10 AM

connection problem

How does Oracle handle block-level corruption, and what are the recovery options?

Oracledetectsandrecoversfromblock-levelcorruptionusingtoolslikeDBVERIFY,RMAN,andDataRecoveryAdvisor,whileofferingrecoveryoptionssuchasblockmediarecovery,standbydatabaserestore,flashbackfeatures,andmanualdatacorrection.Oracleidentifiestwomaintypesofco

Jul 21, 2025 am 01:02 AM

oracle Data Recovery

How can deadlocks occur in Oracle, and how can they be detected and resolved?

Oracle deadlock occurs when two or more sessions wait for each other to release resource locks, forming a circular dependency. For example: 1. After session A updates line 1, try to update line 2; 2. After session B updates line 2, try to update line 1. If it runs at the same time, it will block each other to form a deadlock. Oracle automatically detects and rolls back one of the transactions to break the deadlock, which receives an ORA-00060 error. Other common reasons include not committing transactions holding row-level locks, improper index usage causes lock upgrades, and application logic allows out-of-order overlapping updates. The detection methods include viewing deadlock records in the alert log, tracking files, and querying V$LOCKED_OBJECT and V$SESSION views. The solution is to analyze and track files and ensure transactions

Jul 20, 2025 am 04:08 AM

Oracle死鎖死鎖檢測(cè)解決

How can the BULK COLLECT and FORALL statements improve PL/SQL performance?

BULKCOLLECT and FORALL significantly improve PL/SQL performance by reducing context switching. 1. BULKCOLLECT batch-in-batch data to the set at one time to avoid frequent switching caused by line-by-line acquisition; 2. FORALL sends the DML operations of the set to the SQL engine for processing at one time, replacing inefficient loop execution one by one; 3. The combination of the two can realize efficient data extraction, processing and update, and is suitable for ETL, batch tasks and other scenarios; 4. When using it, pay attention to controlling the set size, rationally use LIMIT batch processing, and avoid adding complex conditional logic to FORALL.

Jul 20, 2025 am 03:58 AM

FORALL

How can Oracle Enterprise Manager (OEM) Cloud Control be used for database monitoring and administration?

Oracle EnterpriseManager(OEM)CloudControl is a comprehensive database operation and maintenance platform that provides centralized management and monitoring functions. 1. Real-time performance monitoring and alarm settings: support viewing key indicators such as CPU, memory, and sessions, setting custom thresholds and automatically triggering email or SNMP notifications, and at the same time, it can analyze historical trend charts to assist in capacity planning; 2. Centralized database management: Unified viewing and maintenance of multiple database instances, support cross-version and cross-platform operations, batch deployment of patches and configurations, and quickly build libraries with templates; 3. Automated maintenance tasks and job scheduling: Integrate RMAN for centralized backup and recovery, create job plans to execute tasks regularly, and control complex processes through the job chain

Jul 20, 2025 am 02:28 AM

Database monitoring

What is table partitioning, and how can it improve performance and manageability for large tables?

Tablepartitioningimprovesperformanceandmanageabilitybysplittinglargetablesintosmallerparts.Itworksbydividingdatabasedonruleslikedaterangesorcategories,enablingqueriestoscanonlyrelevantpartitions.Thisreducesdatascanned,boostsqueryspeed,improvesindexef

Jul 20, 2025 am 01:41 AM

Performance improvements 表分區(qū)

What are the common partitioning methods in Oracle (Range, List, Hash, Composite)?

Oracle provides a variety of partitioning methods to improve performance, manageability, and availability, including scope, list, hash and combined partitions. 1. The range partition divides data according to the range of the value, which is suitable for time-class data. It is necessary to define a clear range. New rows should be inserted into the corresponding partition according to the value; 2. The list partition allocates specific discrete values to each partition, suitable for known categories such as region or status codes, and each partition is independent and unordered; 3. The hash partition evenly distributes data through a hash algorithm, suitable for load balancing, and cannot directly control row distribution, and is often used for primary keys; 4. Combining partitions combine two strategies (such as range plus hash), first partition according to high-level policies and then sub-partitions to achieve finer granular control, suitable for super-large data sets. Choosing the appropriate method depends on the data structure and common query types.

Jul 19, 2025 am 03:48 AM

Partition method Oracle Partition

How are variables and constants declared and used in PL/SQL?

In PL/SQL, both variables and constants are declared in the DECLARE section. The variables can modify the value, while the constants cannot be changed once they are assigned. 1. The variable declaration needs to specify the name and data type, and can be initialized with:= or DEFAULT; 2. The constant must be declared with the CONSTANT keyword and the initial value must be assigned, otherwise an error will be reported in the compilation; 3. The scope of the variables and constants depends on the declaration location, and the inner block can mask the outer variables with the same name; 4. It is recommended to use meaningful names, reasonably group declarations, and use constants first to improve maintainability.

Jul 19, 2025 am 03:48 AM

What are constraints (Primary Key, Foreign Key, Unique, Check, Not Null) in Oracle, and how are they enforced?

Constraints in Oracle databases are rules used to force data integrity and consistency. 1. Primary key constraints ensure that each row is unique and non-empty, and are implemented through a unique index; 2. Foreign key constraints maintain relationships between tables to prevent orphaned records; 3. Unique constraints ensure that the column value is unique but allow a null value; 4. Check the values that can be entered in the constraint limit the column, based on logical expressions; 5. Non-empty constraints prohibit the column from accepting null values, and are often used in combination with other constraints. These constraints are automatically executed when data is inserted, updated or deleted, ensuring data accuracy and reliability.

Jul 19, 2025 am 03:43 AM

Database constraints Oracle約束

What is the purpose of Oracle tablespaces, and how do they relate to data files?

Oracle tablespaces are logical storage containers used to manage the storage of database objects. Each tablespace consists of one or more data files. Its core functions include: 1) organizing storage and allocating user data, indexes, etc. to different table spaces; 2) providing management flexibility and supporting separate backup, recovery or moving table spaces; 3) realizing separation of concerns, such as storing logs and temporary data separately. The tablespace must contain at least one data file, and each data file can only belong to one tablespace. The tablespace capacity can be expanded by adding or adjusting the data file. Common usage scenarios include: increasing table space capacity, placing data according to storage performance requirements, and monitoring space usage. Pay attention to automatic expansion settings, data file quantity management and storage location selection.

Jul 19, 2025 am 12:13 AM

What are views in Oracle, and what are the advantages of using them?

Oracleviewsareusefulbecausetheysimplifycomplexqueries,improvedatasecurity,provideconsistentdatarepresentation,andencapsulatebusinesslogic.1.Theyallowuserstosavecomplexjoinsandcalculationsasreusablequeryobjects,reducingrepetitionanderrors.2.Viewsrestr

Jul 18, 2025 am 03:36 AM

Database view oracle view

How does Oracle's In-Memory Column Store enhance analytical query performance?

Oracle's in-memory columnar storage improves analysis and query performance through columnar storage, efficient compression and SIMD vector processing. Its core advantages include: 1. Column storage reduces I/O and only scans the required columns; 2. Efficient compression reduces memory usage and improves cache efficiency; 3. SIMD technology accelerates aggregation operations and supports real-time analysis; 4. Seamless integration with existing workloads, allowing for updating and analysis without ETL processes.

Jul 18, 2025 am 03:28 AM

oracle 內(nèi)存列存儲(chǔ)

Can you explain the use of ROWNUM and ROWID pseudo-columns in Oracle?

ROWNUM and ROWID are two different pseudo-columns in Oracle databases, with different uses. ROWNUM is the sequential number assigned to each row during query execution, mainly used to limit the result set, such as paging; while ROWID is the physical address identifier of the row, used to quickly access data. When using ROWNUM, you need to pay attention to its allocation before sorting. Therefore, subqueries need to be used to implement ordered paging, and conditions such as ROWNUM=5 or ROWNUM>10 cannot be used directly. ROWID is suitable for debugging, fast positioning of specific rows and temporary identification of duplicate data, but is not recommended for long-term storage because it may change due to row movement. The key difference between the two is the ROWNUM control result set and ROWID optimized data access

Jul 18, 2025 am 02:50 AM

oracle rowid ROWNUM