Oracle 19c vs 26ai Initialization Parameter Comparison | New Features and Deprecated List

In the evolution from Oracle Database 19c to the latest Oracle Database 26ai (FREE), initialization parameters have changed dramatically. In this article, based on the actual show parameter output results in the author’s verification environment (Oracle Database 19c and Oracle Database 26ai FREE), we will thoroughly compare and explain the new feature parameters added, such as AI Vector Search and JavaScript (MLE) support, as well as important parameters that have been deprecated (such as SEC_CASE_SENSITIVE_LOGON).

Note: While parameters in 19c may increase or decrease depending on the application status of Release Updates (RU), this article focuses on the output differences in specific environments.

Conclusion and Shortest Path: Checks to Perform for 26ai Migration
1. Background and Basics: What are the Parameter Changes?
1. What are Initialization Parameters?
2. Trends in Changes: 19c vs 26ai
2. Major Parameters Added in 26ai (23ai-based)
3. Parameters Deprecated or Changed from 19c
4. Execution Examples: Checking and Setting New Feature Parameters
5. Troubleshooting
6. FAQ: Frequently Asked Questions
7. Summary

Conclusion and Shortest Path: Checks to Perform for 26ai Migration

The points that DBAs should check first, which can be read from the parameter differences between 19c and 26ai, are as follows:

Memory Design for AI Functions: Since VECTOR_MEMORY_SIZE is 0 (default), if you use AI Vector Search, review the SGA design and change the settings.
Check the New Language Engine: If using JavaScript in stored procedures, check if MLE_PROG_LANGUAGES is set to ALL.
Authentication Security Corrections: Since SEC_CASE_SENSITIVE_LOGON has disappeared from the parameters (forced enablement), be sure to perform password case-sensitivity connection verification for old applications.
Consideration of Cache Strategy: Consider introducing True Cache for edge use cases.

1. Background and Basics: What are the Parameter Changes?

What are Initialization Parameters?

Initialization parameters are configuration values (spfile / pfile) read when the database starts. They determine the size of memory (SGA/PGA), the functions to be used, and security policies.

Trends in Changes: 19c vs 26ai

The jump from Oracle 19c (Long Term Support) to 23ai/26ai involves not just an increase or decrease in tuning items, but the addition of a massive number of parameters for “incorporating AI and application logic into the database.” On the other hand, legacy security settings tend to be “deprecated (forced application).”

2. Major Parameters Added in 26ai (23ai-based)

Based on actual machine verification, we will explain the particularly important parameters that do not exist in 19c (including the latest RU) but were fully introduced in 26ai (23ai), categorized by function.

AI & Vector Search Related (Most Important)

These are the parameter groups that control vector search (used for RAG construction, etc.), which is the centerpiece feature of Oracle 26ai. These do not exist in 19c.

Parameter Name	Default Value (26ai FREE)	Explanation
VECTOR_MEMORY_SIZE	0	The upper limit of the memory area (in SGA) used for vector indexes and search processing. Setting this is mandatory when using AI search.
VECTOR_QUERY_CAPTURE	ON	Vector search query capture function. Used for tuning and usage analysis.
VECTOR_INDEX_NEIGHBOR_GRAPH_RELOAD	RESTART	Reload policy for the graph structure of vector indexes.

Multilingual Engine (MLE) & For Developers

These relate to the Multilingual Engine (MLE) for executing JavaScript within the database and SQL acceleration.

Parameter Name	Default Value (26ai FREE)	Explanation
MLE_PROG_LANGUAGES	ALL	Programming languages executable within the DB. `ALL` makes JavaScript stored procedures available as standard.
SQL_TRANSPILER	OFF	A function (SQL Transpiler) that transpiles SQL to PL/SQL for acceleration.
JSON_BEHAVIOR	(Empty)	Controls behavior regarding the handling of JSON data.

Performance & Cache (True Cache)

Settings that enhance functions as an application cache.

Parameter Name	Default Value (26ai FREE)	Explanation
TRUE_CACHE	FALSE	Set to `TRUE` when operating the database as an in-memory cache (True Cache).
LOCKFREE_RESERVATION	ON	Lock-free reservation function to improve transaction concurrency.

3. Parameters Deprecated or Changed from 19c

These are parameters that exist in the 19c list but have disappeared (or became invisible) from the 26ai list. This means that “settings can no longer be changed,” which is the number one cause of trouble during migration.

Strictness of Authentication and Security

SEC_CASE_SENSITIVE_LOGON
- 19c: TRUE (Changeable)
- 26ai: Not in list
- Explanation: The setting to disable case sensitivity for passwords (FALSE) has been deprecated. In 26ai, case sensitivity is enforced. Older clients from 10g or earlier, or legacy applications that send passwords only in lowercase, will encounter connection errors.

Audit and Management

UNIFIED_AUDIT_SGA_QUEUE_SIZE
- 19c: 1048576
- 26ai: Not in list
- Explanation: Due to internal architecture changes in Unified Audit, manual control of the queue size is no longer necessary or has been automated.

Others

SERVICE_NAMES
- 19c: orcl
- 26ai: FREE
- This is not a deprecation, but note that the default service name differs by edition. Changes to the connection string (tnsnames.ora) are required.

4. Execution Examples: Checking and Setting New Feature Parameters

Here are the procedures to actually allocate memory for AI Vector Search and enable it in a 26ai environment.

Note: Execute the following SQL with SYSDBA privileges.

Prerequisites:

Oracle Database 26ai (FREE) environment
Connected to CDB$ROOT or PDB

-- 1. Check current Vector related parameters
-- Intent: Check if the feature is enabled by default and what the memory settings are
col name format a40
col value format a20
SELECT name, value 
FROM v$parameter 
WHERE name LIKE 'vector_%';

-- [Execution Result Image]
-- NAME                                     VALUE
-- ---------------------------------------- --------------------
-- vector_memory_size                       0
-- vector_query_capture                     ON
-- ...

-- 2. Allocate SGA memory for Vector Search (Example: 1GB)
-- Explanation: Vector Search requires a dedicated area (Vector Pool) within the SGA.
-- Note: Requires space within SGA_TARGET, or additional physical memory.
ALTER SYSTEM SET vector_memory_size = 1G SCOPE=BOTH;

-- 3. Check if MLE (JavaScript) is enabled
SELECT name, value 
FROM v$parameter 
WHERE name = 'mle_prog_languages';

-- If the result is 'ALL', JavaScript procedures can be created.

5. Troubleshooting

Errors likely to occur due to parameter differences and their solutions.

Error/Phenomenon	Possible Cause	Solution
ORA-01017: Invalid username/password	Due to the deprecation of `SEC_CASE_SENSITIVE_LOGON`, password case is strictly validated.	Correct the client to send the password in the correct case (uppercase/lowercase).
ORA-00922: Invalid option specified	When importing a 19c `pfile`/`spfile`, it included deprecated parameters.	Remove lines with deprecated parameters like `SEC_CASE_SENSITIVE_LOGON` from the parameter file and retry.
ORA-00821: Specified value of sga_target is too small	Allocating memory to new features (like `vector_memory_size`) resulted in insufficient existing `sga_target`.	Perform a design change to increase `sga_max_size` and `sga_target`.

6. FAQ: Frequently Asked Questions

Q1: Can I use the 19c parameter file (pfile) as is in 26ai?
- A1: No, it is not recommended. If deprecated parameters are included, an error will occur during instance startup. Also, default values for directory paths (such as audit_file_dest) differ significantly. Please create a new one or remove deprecated parameters before use.
Q2: How do I disable JavaScript (MLE) in 26ai?
- A2: If you wish to disable it for security reasons, you can restrict it by changing the MLE_PROG_LANGUAGES parameter. However, since some internal functions may depend on it, please check the official documentation.
Q3: What is the value of the compatible parameter?
- A3: In this 26ai FREE environment, compatible is 23.6.0. This implies that 26ai is an extension of the 23ai codebase.

7. Summary

The key points from the Oracle 19c and 26ai initialization parameter comparison are as follows:

AI & Vector Support: Parameters for Generative AI integration, such as VECTOR_MEMORY_SIZE, are the most important additions.
Expansion of Development Languages: JavaScript now runs as standard within the DB due to MLE_PROG_LANGUAGES.
Security Enforcement: The biggest point of caution during migration is that SEC_CASE_SENSITIVE_LOGON has been deprecated, and password case sensitivity is now mandatory.
Cloud & Edge Support: Features for True Cache and edge computing have been enhanced.

When planning a migration, we recommend not just “copying settings,” but redesigning at the parameter level to decide how to utilize (or disable) these new features.

[Note]

The comparison results in this article are based on show parameter output differences in a specific actual machine environment: Oracle Database 19c (Non-CDB/Linux) and Oracle Database 26ai FREE (CDB/Linux).

Depending on the application status of Release Updates (RU) in the 19c environment or the product version of 26ai (Enterprise Edition, etc.), the existence of parameters and default values may differ. Please also refer to the official manuals.

[reference]
Oracle AI Vector Search Parameters