Join us for an exclusive in-person event: Best of Oracle CloudWorld | Ottawa
Thursday, May 8, 2025 at 10:00 a.m.

Eclipsys Blog: Oracle Database (2)

-->

Latest Posts

Sep 2, 2024 2:15:00 PM

Troubleshoot ODA Repo Issue

Oda Oracle database

Introduction If you found previous blog posts helpful for addressing ODA upgrade issues on virtualization platforms, the following article will ease your journey toward the 19.8..

Aug 30, 2024 12:45:00 PM

Securing Your Oracle Database: Step-by-Step Guide to Configuring and Using DBSAT

Oracle Oracle database

Overview: Oracle database allows DML statements to be executed in parallel mode by breaking the DML statements into exclusive smaller tasks. However in releases prior Oracle database 23ai, parallel DML operations had a limitation. Once an object is modified by a parallel DML statement, that object cannot be read or modified by later statements of the same transaction before ending the transaction by executing commit or rollback. Oracle Database 23ai removes that restriction and by introducing “Unrestricted Parallel DMLs or Unrestricted Direct Loads” feature. Benefits: In the same transaction session and before ending the transaction, you can: Query the same table multiple times Perform serial or parallel DML on the same table Perform multiple direct loads Overhead Reduced Enable parallel DML in a session Separate commits are not required after each parallel DML statement Take the full advantage of using parallel DMLs in the same transaction Restrictions: Heap organized table only. No ASSM tablespaces How to Enable Parallel DML Mode: The parallel DML mode is required because parallel DML and serial DML have different locking, transaction, and disk space requirements and parallel DML is disabled for a session by default. When parallel DML is disabled, no DML is executed in parallel even if the PARALLEL hint is used. When parallel DML is enabled in a session, all DML statements in this session are considered for parallel execution. Run below SQL statement to enable parallel DML mode in a session: ALTER SESSION ENABLE PARALLEL DML; Enable unrestricted parallel DML mode in a specific SQL statement, include the ENABLE_PARALLEL_DML hint. INSERT /*+ ENABLE_PARALLEL_DML */ … However, even if parallel DML is enabled, the DML operation may still execute serially if there are no parallel hints or no tables with a parallel attribute or if restrictions on parallel operations are violated. Practice: In this practice, I’ll enable parallel DML and perform a parallel insert (non-unrestricted) without commit or rollback. After the insert, I’ll run a select from the same table and it will cause an error. Then I’ll perform the parallel insert using unrestricted parallel hint without commit or rollback, After I’ll run select and additional insert without errors. 1. Create a new table. SQL> create table test_dmls as select * from objects_objects; Table TEST_DMLS created. 2. Alter the session and enable parallel DML. SQL> alter session enable parallel dml; Session altered. 3. Insert into the table with PARALLEL hint. SQL> insert /*+ parallel(test_dmls 4) */ into test_dmls select /*+ parallel(test_dmls 4) */ * from test_dmls; 76,237 rows inserted. 4. Select from the table without performing a commit or rollback. You will get and error. SQL> select count(*) from test_dmls; Error starting at line : 1 in command - select count(*) from test_dmls SQL ORA-12838: cannot read/modify an object after modifying it in parallel More Details : https://docs.oracle.com/error-help/db/ora-12838/ SQL> !oerr ora 12838 12838, 00000,

commit; Commit complete. 6. After the commit is done, now you can select again from the table. SQL> select count(*) from test_dmls; COUNT(*) ___________ 152474 7. Perform a parallel insert using ENABLE_PARALLEL_DML hint. SQL> insert /*+ enable_parallel_dml(test_dmls 4) */ into test_dmls select /*+ enable_parallel_dml(test_dmls 4) */ * from test_dmls; 152,474 rows inserted. 8. Select from the table without performing a commit or rollback. Now you will NOT get an error. SQL> select count(*) from test_dmls; COUNT(*) ___________ 304948 9. Perform another parallel insert without a commit or rollback. No error. SQL> insert /*+ enable_parallel_dml(test_dmls 4) */ into test_dmls 2* select /*+ enable_parallel_dml(test_dmls 4) */ * from test_dmls; 304,948 rows inserted. SQL> / 609,896 rows inserted. SQL> / 1,219,792 rows inserted. SQL> select count(*) from test_dmls; COUNT(*) ___________ 2439584" loading="lazy">

Aug 20, 2024 1:00:00 PM

Oracle 23ai: Unrestricted Parallel DMLs

Oracle database Oracle 23ai

Overview: Oracle database allows DML statements to be executed in parallel mode by breaking the DML statements into exclusive smaller tasks. However, in releases prior to Oracle..

Aug 19, 2024 11:00:00 AM

How to Chat with MySQL Database in Natural Language (English)

Oracle database Mysql Open ai

Aug 14, 2024 4:11:00 PM

Migration of On-Premises Oracle 18c PDB to OCI 19c PDB using Full Transportable Tablespace

Oracle database Oci

Introduction Migrating an Oracle database from on-premises to Oracle Cloud Infrastructure (OCI) involves several steps to ensure a smooth transition while minimizing downtime. The..

Jul 23, 2024 4:08:00 PM

Measuring Storage Performance for Oracle Database

Oracle Oracle database Databases Orion

Introduction Storage vendors often provide extensive product performance data, but this information may not accurately predict how the storage will perform with an Oracle..

Jul 23, 2024 4:06:00 PM

Exadata Exascale and What it Means for Your Oracle Workloads

Exacc Oracle database Exadata

Last week, Oracle Exadata Exascale was released, and it is one of the features that I have been most excited about in a while. I will be writing a couple of blogs around the..

Jul 10, 2024 5:17:00 PM

Oracle Database 23ai: Fetch Top-N Rows Per Group Queries

Oracle Oracle database Oracle 23ai Oracle database 23ai

Overview: Oracle 23ai introduces partition by clause in fetch first clause to get top-N rows per group. A query’s syntax SELECT …….. FROM …….. ORDER BY , FETCH FIRST , ROWS ONLY..

Jun 23, 2024 5:24:00 PM

Oracle 23ai: JSON Schema Support

Oracle Oracle database Oracle 23ai Oracle database 23ai Json

Overview: Oracle first introduced the ability to display a JSON schema when they introduced the JSON Data in Oracle 12.2 but without the option to validate the structure of JSON..

Jun 4, 2024 5:58:00 PM

ODA Bare Metal Patching From 19.16 to 19.20

Oda Oracle Oracle database Databases

ODA Upgrade from 19.16 to 19.20 Patching Oracle Database Appliance (ODA) Bare Metal Systems involves applying updates to both the operating system and Oracle Software Components...