Introduction
1. New Features in Security
2. Intelligent Query Processing (IQP) Enhancements
3. Important Improvements in Storage and File Management
4. Backup & Restore – New Generation
5. Agent, Automation and Governance
6. Smart Management of Memory, CPU and IO
7. New Features in High Availability and Disaster Recovery
8. Monitoring and Observability
9. Other Important Features for DBAs
Summary Table — SQL Server 2025 Key Enhancements
Conclusion
SQL Server 2025 Upgrade Checklist
References

Introduction

SQL Server 2025 (version 17.x, officially released in November 2025 and now generally available) is one of the most advanced and feature-rich updates Microsoft has delivered in the last decade. This release introduces major improvements in security, performance tuning, high availability, automation, and native AI integration. With these enhancements, SQL Server is no longer just a traditional relational engine—it becomes a modern, intelligent, and enterprise-ready data platform.For DBAs, the 2025 version provides stronger security controls, deeper observability, faster troubleshooting tools, smarter query processing, and better support for hybrid and cloud scenarios. It also enables secure interaction with REST APIs and AI services, opening new possibilities for automation and data processing that were not possible in earlier versions.This document gives a detailed review of all key DBA-focused features. Each section explains what is new, why it matters, and how it can be used in real environments. The information is based on official Microsoft documentation (“What’s New in SQL Server 2025”) combined with practical experience and real-world testing.

1. New Features in Security

SQL Server 2025 brings a stronger Secure by Default model built on modern Zero Trust principles. Security is improved at every layer, from authentication and encryption to access control and auditing. These upgrades help organizations reduce the risk of credential attacks, improve compliance, and protect sensitive data without adding complexity to daily DBA tasks.

1.1 Role-Based Access Control (RBAC) Enhancements

SQL Server 2025 introduces several new built-in roles designed for modern workloads, including AI services, external REST calls, and external model execution. These roles follow the least privilege principle and help DBAs delegate sensitive operations safely.
Examples include roles for API execution or AI model usage (exact names depend on the final Microsoft release).
.

Why It Matters

Reduces the need for high-privilege accounts
Helps meet compliance standards (GDPR, HIPAA, ISO)
Simplifies permission management in hybrid and AI-driven environments

Test example:

-- Create login and user
CREATE LOGIN ai_service_login WITH PASSWORD = 'StrongPass!2025';
CREATE USER ai_service_user FOR LOGIN ai_service_login;

-- Grant a limited AI role (example name)
ALTER ROLE db_ai_executor ADD MEMBER ai_service_user;

-- Test delegated execution
EXEC AS USER = 'ai_service_user';
EXEC sp_invoke_external_rest_endpoint @url = 'https://api.openai.com/...';
REVERT;

1.2 OAuth and Managed Identity Support (Azure-Compatible Security)

SQL Server 2025 supports Managed Identity (MI) for secure, keyless authentication when the server is Azure Arc–enabled. MI can be used for backups to Azure Blob Storage, accessing Azure Key Vault, and making secure outbound REST calls. Authentication is handled through short-lived tokens instead of stored credentials.
.

Why It Matters

Removes the need to store secrets or access keys
Automatically rotates credentials
Greatly improves hybrid security
Reduces administrative overhead for backups and external connections

Test example:

-- Conditional masking
ALTER TABLE Customers 
    ALTER COLUMN Email
        ADD MASKED WITH (
            FUNCTION = 'partial(1,"XXX@",0)',
            CONDITION = 'CURRENT_USER() <> ''admin'''
        );

-- Normal users see masked data
SELECT Email FROM Customers;

1.3 Advanced Dynamic Data Masking

Dynamic Data Masking (DDM) in SQL Server 2025 is more flexible. It now supports:

Conditional masking based on roles or user context
More advanced partial-masking patterns
Better integration with Always Encrypted, including pattern search on masked columns

Why It Matters

Protects sensitive information (PII) in real-time
Allows safe access for developers, testers, and reporting systems
Improves compliance without changing application logic

Test example:

-- Conditional masking
ALTER TABLE Customers 
    ALTER COLUMN Email
        ADD MASKED WITH (
            FUNCTION = 'partial(1,"XXX@",0)',
            CONDITION = 'CURRENT_USER() <> ''admin'''
        );

-- Normal users see masked data
SELECT Email FROM Customers;

1.4 Improvements in Auditing and Encryption

SQL Server 2025 enhances several core security components:

Auditing: New actions for REST calls, AI functions, vector operations; improved performance; support for cold/archived audit logs
PBKDF2 Password Hashing: SQL logins now default to PBKDF2 with 100,000 iterations and SHA-512, making password cracking significantly harder
Always Encrypted Enhancements:
- More supported operations (including pattern matching)
- Stronger RSA padding (OAEP-256)
- TLS 1.3 and TDS 8.0 enabled by default for major features (AG, Replication, etc.)

Why It Matters

Stronger protection against brute-force and credential-stuffing attacks
Better transparency and traceability for security monitoring
Improved security posture by default—less manual configuration for DBAs

Test example:

-- New login using PBKDF2 hashing
CREATE LOGIN test_login WITH PASSWORD = 'StrongPass2025!';

SELECT name, password_hash 
    FROM sys.sql_logins 
    WHERE name = 'test_login';

-- Audit external REST calls
CREATE SERVER AUDIT REST_Audit TO FILE (FILEPATH = 'C:\Audits\');
CREATE SERVER AUDIT SPECIFICATION REST_Spec
    FOR SERVER AUDIT REST_Audit
        ADD (EXECUTE ON sp_invoke_external_rest_endpoint BY PUBLIC);

ALTER SERVER AUDIT REST_Audit WITH (STATE = ON);

2. Intelligent Query Processing (IQP) Enhancements

SQL Server 2025 continues to expand the Intelligent Query Processing (IQP) framework. IQP is designed to improve performance automatically, without requiring application changes or manual tuning. Most IQP features are enabled by default under compatibility level 170, making it easier for DBAs to benefit from them immediately. The enhancements in this version help reduce issues such as parameter sniffing, memory misallocation, inaccurate cardinality estimates, and excessive parallelism.

2.1 Advanced Adaptive Plan Optimization

SQL Server 2025 introduces more powerful adaptive mechanisms that adjust execution plans while the query is running. These include:

Adaptive Join Switching: The engine can switch between join types (Hash Join ↔ Nested Loops) based on actual row counts.
Memory Grant Feedback (3rd Generation): Provides more accurate adjustments to memory grants to avoid spills and unnecessary memory usage.
Optional Parameter Plan Optimization (OPPO): Creates separate execution plans for NULL and non-NULL parameter values—especially useful for optional or highly selective parameters.

Why It Matters

More stable performance across variable workloads
Fewer recompilations
Less need for hints or manual plan forcing
Better behavior for queries with optional filters

Test example:

-- Optional parameter scenario
CREATE PROCEDURE GetOrders @CustomerID INT = NULL
AS
    SELECT * 
        FROM Orders
        WHERE (@CustomerID IS NULL OR CustomerID = @CustomerID);
GO

-- Different executions build different plans under OPPO
EXEC GetOrders @CustomerID = 123;  -- Typically uses an index seek
EXEC GetOrders;                    -- Uses a scan for NULL

-- View plans in Query Store
SELECT plan_id, reason, last_execution_time
    FROM sys.query_store_plan
    WHERE query_id = (
        SELECT query_id 
            FROM sys.query_store_query 
            WHERE query_text LIKE '%GetOrders%'
    );

2.2 Cardinality Estimation 3.0

SQL Server 2025 introduces Cardinality Estimator (CE) 3.0, improving row-count estimation for:

Skewed or uneven data distributions
Nullable columns and complex predicates
Expressions such as CASE, computed columns, and scalar functions
CE Feedback for expressions, allowing SQL Server to correct misestimates automatically.

Why It Matters

More accurate plans
Better join ordering
Reduced risk of poor estimates that lead to bad performance
Improved stability without hinting or manual statistics adjustments

Test example:

-- Example with skewed data
CREATE TABLE Sales (
    Region VARCHAR(50), 
    Amount DECIMAL(10,2)
);

INSERT INTO Sales VALUES ('North', 100000), ('South', 150);

SELECT Region, SUM(Amount)
    FROM Sales
    WHERE Region = 'North'
    GROUP BY Region;

-- After several executions, CE Feedback helps adjust cardinality
-- View CE feedback info
SELECT reason, feedback_state_desc
    FROM sys.query_store_plan_feedback;

2.3 Smart Parallelism

SQL Server 2025 includes new parallelism optimizations such as:

- - Degree of Parallelism (DOP) Feedback : Adjusts DOP automatically based on past executions. If a query shows excessive overhead, the engine reduces the parallelism level for future runs.
  - Dynamic Thread Rebalancing : Distributes work more evenly across threads during execution.
  - Workload-Level Auto-Tuning : Automatically selects optimal MaxDOP settings under different workloads.

Why It Matters

Reduces waits like CXPACKET and CXCONSUMER
Prevents unnecessary high-DOP executions
Better performance on multi-core CPUs without manual tuning
Improves overall server throughput

Test example:

-- Parallel workload
SELECT COUNT(*) 
    FROM LargeTable
    GROUP BY Category;

-- View DOP Feedback via Query Store
SELECT query_id, plan_id, reason
    FROM sys.query_store_plan
    WHERE reason LIKE '%DOP%';

2.4 Optimized Locking and Concurrency

SQL Server 2025 introduces Optimized Locking, which improves concurrency through:

TID Locking (Transaction ID Locking) : Keeps only one lock per transaction, releasing other locks earlier during execution.

Lock After Qualification (LAQ) : Locks rows after predicate evaluation, not before, reducing lock contention during scans.

These features require Accelerated Database Recovery (ADR) and are enabled at the database level. Why It Matters

Significant reduction in blocking during heavy OLTP workloads
Lower lock memory usage
Fewer lock escalations
Better performance without application changes

Test example:

ALTER DATABASE CURRENT SET ACCELERATED_DATABASE_RECOVERY = ON;
ALTER DATABASE SCOPED CONFIGURATION SET OPTIMIZED_LOCKING = ON;

-- Session 1
BEGIN TRAN;
UPDATE LargeTable 
        SET Value = 1 
    WHERE ID % 100 = 0;  -- Holds transaction open

-- Session 2
SELECT *
    FROM LargeTable
    WHERE ID % 100 = 1;  -- Less blocking with LAQ/TID

-- Investigate locks
SELECT resource_type, request_mode, request_status
    FROM sys.dm_tran_locks;

3. Important Improvements in Storage and File Management

SQL Server 2025 introduces several important enhancements in the storage layer, with a strong focus on improving the reliability and efficiency of tempdb. Since tempdb is one of the most frequently used system databases, even small optimizations can have a major impact on overall performance. In this release, the new features reduce contention, improve space governance, and simplify storage management—especially in high-concurrency or multi-tenant environments.

3.1 TempDB Intelligent Allocation

SQL Server 2025 continues the long-term improvements made in previous versions (PFS fixes in SQL Server 2019 and GAM/SGAM optimizations in 2022) and introduces new capabilities that make tempdb more predictable under heavy workloads:

Tempdb Space Resource Governance

Using Resource Governor, SQL Server can now limit the amount of tempdb space consumed by each workload group. This prevents scenarios where one workload floods tempdb and disrupts other sessions.

Lower Contention on Allocation Maps

Improvements in allocation algorithms reduce bottlenecks in PFS, GAM, and SGAM pages, providing better parallel performance.

Auto-balancing Behavior for Files

While proportional fill is still used, governance ensures that uneven file sizes are less harmful. DBAs still need to size files evenly, but the risk of runaway allocation is reduced.

Tmpfs Support for Linux Deployments

SQL Server on Linux can now place tempdb files on tmpfs, a memory-backed filesystem. This significantly reduces latency for operations that rely heavily on tempdb, such as large sorts, hash joins, and spill events.

Why It Matters for DBAs

Stronger isolation between workloads
Lower risk of tempdb running out of space
Better performance for parallel operations
Faster tempdb on Linux with RAM-backed storage
Less manual tuning required

Test example:

-- Define Resource Governor rules for tempdb control
CREATE RESOURCE POOL rp_LimitedTempDB WITH (MAX_IOPS_PER_VOLUME = 2000);
CREATE WORKLOAD GROUP wg_LimitedTempDB USING rp_LimitedTempDB;

ALTER RESOURCE GOVERNOR RECONFIGURE;

-- Enable ADR for tempdb (requires SQL Server restart)
ALTER DATABASE tempdb SET ACCELERATED_DATABASE_RECOVERY = ON;

-- Example: relocating tempdb files to tmpfs on Linux
ALTER DATABASE tempdb MODIFY FILE (
    NAME = tempdev,
    FILENAME = '/tmpfs/tempdb.mdf'
);

3.2 Faster Snapshots and Copy-on-Write

SQL Server 2025 does not introduce a new snapshot engine, but several underlying improvements result in faster and more efficient snapshot-based operations:

ADR Enhancements

Accelerated Database Recovery reduces the volume of versioning work stored in tempdb. This indirectly improves snapshot and copy-on-write performance.

Storage Subsystem Improvements

When tempdb is placed on tmpfs (Linux) or fast NVMe devices (Windows), snapshot isolation workloads experience reduced latency.

Better Coordination with Version Store

Version store operations—used by snapshot isolation, READ COMMITTED SNAPSHOT, and online indexing—are more efficient due to optimized space management.

Why It Matters for DBAs

Faster queries using snapshot isolation
Reduced tempdb pressure in read-heavy workloads
Better performance for ETL processes and long-running reports
Lower I/O cost during versioning

Test example:

-- Creating a database snapshot (faster with ADR enabled)
CREATE DATABASE AdventureWorks_Snapshot
ON (
    NAME = AdventureWorks_Data,
    FILENAME = 'C:\Snapshots\AW_2025.ss'
)
AS SNAPSHOT OF AdventureWorks;

4. Backup & Restore – New Generation

SQL Server 2025 introduces a new generation of backup and restore capabilities, focusing on performance, security, and cloud readiness. Many of the enhancements aim to reduce the workload on the primary replica, lower backup storage costs, and protect backups against modern threats such as ransomware. All major features in this area are now Generally Available (GA) and fully supported for production environments.

4.1 Advanced Backup Enhancements

SQL Server 2025 delivers multiple improvements that significantly enhance backup performance and resiliency:

Full, Differential, and Log Backups on Secondary Replicas

Unlike earlier versions (where secondary backups were mostly copy-only), SQL Server 2025 fully supports running all backup types on secondary replicas in an Always On Availability Group. This offloads I/O workload from the primary and improves overall system responsiveness.

ZSTD Compression Algorithm

The new Zstandard (ZSTD) compression offers better ratios and faster processing compared to MS_XPRESS.

It supports three levels:

- - LOW (default – fast, balanced)
  - MEDIUM (better ratio)
  - HIGH (maximum compression, slightly higher CPU)

Immutable Backups in Azure Blob Storage

SQL Server can now write backups into Azure immutability-enabled containers, preventing accidental or malicious deletion or modification—an essential defense against ransomware.

Backup to URL Using Managed Identity

When SQL Server is Azure Arc–enabled, backups can authenticate to Azure Blob Storage using Managed Identity (MI). This removes the need for SAS tokens or SQL credentials.

Why It Matters for DBAs

Reduced load on production servers
Faster, smaller backups
Stronger protection against ransomware and insider threats
Easier and more secure cloud integration
Lower operational complexity

Test example:

-- Backup using ZSTD compression
BACKUP DATABASE AdventureWorks
    TO DISK = 'C:\Backups\AW.bak'
    WITH COMPRESSION (ALGORITHM = ZSTD, LEVEL = MEDIUM), STATS = 10;

-- Full backup on a secondary replica in Availability Group
BACKUP DATABASE AdventureWorks
    TO DISK = '\\shared\backups\AW_full_secondary.bak'
    WITH FORMAT, INIT;

-- Immutable backup to Azure Blob Storage
BACKUP DATABASE AdventureWorks
    TO URL = 'https://storageaccount.blob.core.windows.net/container/AW_immutable.bak'
    WITH FORMAT, STATS = 10;

-- Backup to URL using Managed Identity (Azure Arc)
BACKUP DATABASE AdventureWorks
    TO URL = 'https://storageaccount.blob.core.windows.net/container/AW_mi.bak';

4.2 Improvements in Online Restore

While SQL Server 2025 does not introduce a new online restore framework, several underlying improvements enhance restore performance and reliability:

Faster Checksums and Hardware-Accelerated Validation

Integrated with ZSTD and new CPU instruction sets, restore operations can complete checksum verification more quickly.

Better Corruption Detection During Restore

SQL Server identifies problematic pages sooner, reducing wasted restore time.

More Efficient Partial/Filegroup Restore

These operations benefit from the improved recovery process, especially when ADR (Accelerated Database Recovery) is enabled.

Why It Matters for DBAs

Less downtime in critical restore scenarios
Faster validation of backup integrity
More predictable recovery operations

Test example:

RESTORE DATABASE AdventureWorks
    FROM DISK = 'C:\Backups\AW.bak'
    WITH CHECKSUM, STATS = 10;

4.3 Automatic Background Corruption Checks

SQL Server 2025 improves internal integrity checks, especially around checksum validation and early error detection. While some advanced corruption detection features remain Azure-only, on-premises SQL Server benefits from:

Faster execution of DBCC CHECKDB
Improved version store stability (due to ADR enhancements)
Stronger default checksum validation

Why It Matters for DBAs

Early detection of failing storage or corrupted pages
Reduced chance of silent data corruption
More efficient maintenance windows

Test example:

-- Ensure database uses checksum protection
ALTER DATABASE AdventureWorks SET PAGE_VERIFY CHECKSUM;

-- Improved CHECKDB performance in SQL Server 2025
DBCC CHECKDB ('AdventureWorks') WITH NO_INFOMSGS, ALL_ERRORMSGS;

5. Agent, Automation and Governance

SQL Server 2025 introduces only a small number of changes in the areas of automation and governance. Most of the major innovations rely on external platforms such as Azure Arc, Microsoft Fabric, or DevOps tooling. SQL Server Agent, Policy-Based Management, and System Insights remain largely unchanged in this release. However, several enhancements in monitoring, prediction, and integration offer better end-to-end governance when SQL Server is used as a hybrid or cloud-connected environment.

5.1 Smart SQL Agent Jobs

SQL Server 2025 does not introduce a new intelligent scheduling engine for SQL Agent. Features such as adaptive job frequency, automated throttling based on CPU load, or predictive job completion time are still not built into the engine.SQL Agent continues to support:

- Standard frequency schedules (daily, weekly, monthly)
- Idle CPU conditions
- Alert-based execution
- Integration with PowerShell and external automation

If DBAs need advanced automation—such as scaling schedules based on system load—they must rely on Azure Automation, PowerShell, or third-party orchestration tools. Why It Matters for DBAs SQL Agent remains reliable and stable, but automation at scale continues to depend on external services. Hybrid DBAs will benefit more from Azure Automation, Logic Apps, and GitHub Actions

Test example(standard schedule):

-- Create a standard SQL Agent job with a daily schedule
EXEC msdb.dbo.sp_add_job @job_name = 'Nightly Maintenance';

EXEC msdb.dbo.sp_add_jobschedule 
    @job_name = 'Nightly Maintenance',
    @name = 'Daily Schedule',
    @freq_type = 4,           -- Daily
    @active_start_time = 020000;  -- 02:00 AM

5.2 System Insights (Enhanced Predictive Monitoring)

System Insights first appeared in SQL Server 2019. SQL Server 2025 provides minor enhancements, mainly around:

- Better prediction of CPU bottlenecks
- Detection of log write delays
- Tempdb pressure forecasting
- Improved learning models when connected to Fabric or Azure Monitor

There is no full “vNext” version of System Insights in 2025, but predictive quality improves due to updated models and tighter integration with cloud analytics. Why It Matters for DBAs DBAs gain more accurate early warnings for performance issues without installing extra software. Combined with Query Store, this provides a proactive operations model.

Test example:

-- Enable external scripts (required for System Insights)
EXEC sp_configure 'external scripts enabled', 1;
RECONFIGURE;

-- Review the performance indicators exposed by System Insights
SELECT * 
    FROM sys.dm_os_performance_counters 
    WHERE counter_name LIKE '%System Insights%';

5.3 Governance and GitOps Integration

SQL Server 2025 does not include native GitOps capabilities such as storing instance configurations in Git or automatic drift detection. However, when SQL Server is connected through Azure Arc, administrators can use:

- Azure Policy for configuration governance
- GitOps (Flux) for Kubernetes-based SQL MI deployments
- Desired State Configuration (DSC) for Windows-based SQL instances

On standalone SQL Server installations, DBAs can use SSMS Git integration, dbatools, or configuration export scripts. Why It Matters for DBAs This allows governance models similar to DevOps pipelines—version-controlled configurations, automatic drift detection, and repeatable deployments, but through external platforms, not SQL Server itself.

Test example(dbatools export for GitOps):

# Export SQL Server instance configuration
Export-DbaInstance -SqlInstance "ServerName" -Path "C:\Git\Config"
# Then commit files to Git for drift detection

5.4 Built-in AI Assistance for DBAs

SQL Server 2025 does not include fully built-in AI for index recommendations or anomaly detection. These features remain part of:

Azure SQL Intelligent Performance
SQL Database Advisor
Microsoft Copilot in Azure and SSMS
Fabric Monitoring

However, SQL Server 2025 significantly improves:

Query Store regression detection
Plan comparison tools in SSMS 20+
AI-assisted suggestions through GitHub Copilot in SSMS
Telemetry shared with Azure Monitor (when enabled)

This gives DBAs semi-automated tuning support without embedding AI inside the engine. Why It Matters for DBAs Although the engine does not automate tuning, the surrounding ecosystem provides powerful AI guidance, helping DBAs detect regressions faster and implement safer tuning actions

Test example(Query Store regression detection):

-- Enable Query Store if not already enabled
ALTER DATABASE CURRENT SET QUERY_STORE = ON;

-- Detect performance regressions
SELECT *
    FROM sys.query_store_plan
    WHERE regression_status_desc IS NOT NULL;

6. Smart Management of Memory, CPU and IO

SQL Server 2025 introduces several practical improvements in how the engine manages memory, CPU, and storage I/O. These enhancements do not form a new subsystem such as “Intelligent Memory Manager” or “IO Hotspot Predictor,” but they significantly improve performance in real workloads. Most of these improvements come through Intelligent Query Processing (IQP), the third-generation Memory Grant Feedback, and a more adaptive buffer pool.

6.1 Intelligent Memory Manager

SQL Server 2025 enhances memory management in three key areas:

1. Third-Generation Memory Grant Feedback

The new version refines Memory Grant Feedback with better detection of over-allocation and under-allocation. Memory grants adjust more accurately based on runtime statistics, reducing:

- - - Disk spills (e.g., “Sort Spills”, “Hash Spills”)
    - Excessive memory consumption by a single query
    - Competition between large and small workloads

1. Smarter Buffer Pool Eviction

SQL Server now uses improved algorithms to determine which pages should stay in the buffer pool:

- - - Frequently used (hot) pages remain cached longer.
    - Rarely used (cold) pages are evicted earlier.
    - This reduces repeated I/O and improves read performance.

1. Better Memory Broker Behavior

Although SQL Server 2025 does not introduce dynamic buffer pool resizing, improvements in memory broker logic and the raised memory cap for Standard Edition (up to 256 GB) result in:

- - - More predictable memory distribution
    - Less sudden pressure during peak workloads
    - Fewer stalls on large analytical queries

Why It Matters for DBAs These enhancements lead to:

Lower memory pressure under mixed workloads
More stable query behavior
Fewer tempdb spills and less I/O amplification

Reduced tuning overhead for DBAs

Test example:

-- Check memory grants and feedback status
SELECT  mg.session_id,
        mg.requested_memory_kb,
        mg.granted_memory_kb,
        mg.used_memory_kb,
        mg.is_feedback_available
    FROM sys.dm_exec_query_memory_grants AS mg
    WHERE mg.is_feedback_available = 1;

-- Check buffer pool cached pages
SELECT  COUNT(*) AS CachedPages,
        (COUNT(*) * 8) / 1024 AS CachedMB
    FROM sys.dm_os_buffer_descriptors;

6.2 IO Latency Management and Monitoring

SQL Server 2025 improves I/O reliability and efficiency with several enhancements:

1. Better I/O Behavior through IQP and Buffer Pool Improvements

Although SQL Server does not implement explicit “I/O hotspot prediction,” improvements in:

- - - Memory Grant Feedback
    - Optimized Locking
    - Buffer pool eviction algorithms
    - Tempdb enhancements (including tmpfs support on Linux)

help reduce unnecessary read/write patterns and lower I/O latency.

1. Lower Latency for Frequently Accessed Pages

Smarter page residency decisions help SQL Server:

- - - Keep hot pages in memory
    - Reduce trips to storage
    - Lower PAGEIOLATCH waits on busy systems

1. Improved I/O Visibility through DMVs

SQL Server 2025 enhances monitoring tools rather than adding automatic alerts. The DMV sys.dm_io_virtual_file_stats remains the primary source for diagnosing:

- - - High-latency disks
    - Slow log drives
    - Uneven file distribution
    - Aging SSD or cloud volumes

DBAs can build alerts or dashboards based on these metrics.

Note:

SQL Server 2025 still does not support online movement of data or log files between drives. It remains an offline operation.

Why It Matters for DBAs

Lower average latency for OLTP systems
Better throughput in highly concurrent workloads
Clearer visibility into which files cause bottlenecks

Faster troubleshooting with accurate DMV metrics

Test example:

-- Check I/O latency per file with physical file paths
SELECT  DB_NAME(vfs.database_id) AS DatabaseName,
        mf.physical_name AS FilePath,
        vfs.io_stall_read_ms / NULLIF(vfs.num_of_reads, 0) AS AvgReadLatencyMs,
        vfs.io_stall_write_ms / NULLIF(vfs.num_of_writes, 0) AS AvgWriteLatencyMs,
        vfs.num_of_reads AS TotalReads,
        vfs.num_of_writes AS TotalWrites
    FROM sys.dm_io_virtual_file_stats(NULL, NULL) AS vfs
        JOIN sys.master_files AS mf
            ON vfs.database_id = mf.database_id
                AND vfs.file_id = mf.file_id
    WHERE vfs.num_of_reads > 0 OR vfs.num_of_writes > 0
    ORDER BY AvgReadLatencyMs DESC, AvgWriteLatencyMs DESC;

7. New Features in High Availability and Disaster Recovery

SQL Server 2025 introduces several enhancements that improve reliability, reduce downtime, and increase performance across both synchronous and asynchronous HA/DR architectures. These features make Always On Availability Groups more efficient and expand hybrid-cloud capabilities through deeper integration with Microsoft Fabric. The overall result is a more resilient and scalable platform for mission-critical workloads

7.1 Always On Enhancements – 2025 Generation

SQL Server 2025 includes multiple engine-level improvements for Availability Groups (AGs):

Faster Failover with Transaction Replay Caching

A new caching mechanism speeds up replaying log records during failover. This reduces the time required for secondary replicas to catch up, resulting in noticeably shorter failover durations.

Improved Synchronous Commit and Read-Scale Performance

Enhancements to sync commit and asynchronous batch dispatching improve replication efficiency. This lowers latency and increases throughput for readable secondary replicas.

Backups on Secondaries (Full, Differential, Log)

AG replicas can now run full, differential, and log backups—not only copy-only backups. This offloads overhead from the primary server and supports better operational distribution.

Query Store Enabled by Default on Readable Secondaries

Query Store automatically runs in read-write mode on readable secondaries, allowing full plan capture, regression detection, and troubleshooting without relying on the primary.

Why It Matters for DBAs

Faster failovers → lower RTO
More balanced workloads → lower pressure on primary
Full monitoring on secondaries → better diagnostics in HA setups
More flexible backup strategies → simpler maintenance windows

Test example:

-- Create Availability Group (primary)
CREATE AVAILABILITY GROUP MyAG
    WITH (DISTRIBUTED = OFF)
    FOR DATABASE AdventureWorks
    REPLICA ON 'PrimaryServer' WITH (
        ENDPOINT_URL = 'TCP://primary:5022',
        AVAILABILITY_MODE = SYNCHRONOUS_COMMIT,
        FAILOVER_MODE = AUTOMATIC
    ),
    'SecondaryServer' WITH (
        ENDPOINT_URL = 'TCP://secondary:5022',
        AVAILABILITY_MODE = SYNCHRONOUS_COMMIT,
        SECONDARY_ROLE (ALLOW_CONNECTIONS = READ_ONLY)
    );

-- Query Store on secondary (default in 2025)
ALTER DATABASE AdventureWorks
    SET QUERY_STORE = ON (OPERATION_MODE = READ_WRITE);

-- Backup on secondary
BACKUP DATABASE AdventureWorks TO DISK = 'N:\Backups\AW.bak';

7.2 Distributed AG (DAG) – vNext Improvements

Distributed Availability Groups receive internal optimizations:

Lower-latency log transport through improved flow control.
Unified Commit Stream (UCS) batching for more efficient forwarding.
Better support for hybrid topologies (on-premises + Azure SQL MI or Arc-enabled SQL).

Why It Matters for DBAs

Easier cross-region or multi-datacenter HA/DR.
More stable performance in globally distributed architectures.
Better alignment with hybrid-cloud disaster recovery strategies.

Test example:

-- Join AGs into a Distributed AG
ALTER AVAILABILITY GROUP MyAG JOIN AVAILABILITY GROUP DistributedAG;
ALTER AVAILABILITY GROUP DistributedAG 
    ADD LISTENER 'DistListener' ('192.168.1.100');

7.3 Accelerated Database Recovery (ADR) Improvements

ADR continues to evolve in SQL Server 2025:

Faster rollback of long-running transactions using persistent version store.
Lower transaction log growth during large operations.
ADR is now active in tempdb, reducing rollback and cleanup delays for tempdb workloads.

Why It Matters for DBAs

Faster recovery after failover or cancellation.
Fewer large-rollbacks blocking resources.
More stable environments with heavy tempdb usage

Test example:

ALTER DATABASE AdventureWorks 
    SET ACCELERATED_DATABASE_RECOVERY = ON;

-- Check ADR status for tempdb
SELECT  name, is_accelerated_database_recovery_on 
    FROM sys.databases 
    WHERE name = 'tempdb';

7.4 Real-Time Mirroring to Microsoft Fabric

SQL Server 2025 introduces native mirroring of relational data to Microsoft Fabric:

Data is streamed into OneLake as Delta Parquet tables.
Zero-ETL architecture: real-time analytics without complex pipelines.
Resource Governor limits can prevent heavy workloads from overwhelming the OLTP server.

Why It Matters for DBAs

Real-time analytics with almost zero overhead on primary systems.
Simple configuration for hybrid operational + analytics environments.
Reduced need for ETL-based data movement tools.

Test example:

-- Enable mirroring to Fabric
CREATE DATABASE MIRROR FOR DATABASE AdventureWorks
    TO FABRIC 'myfabricworkspace'
    WITH (
        LAKEHOUSE = 'MyLakehouse',
        RESOURCE_GOVERNOR_WORKLOAD_GROUP = 'AnalyticsGroup'
    );

8. Monitoring and Observability

SQL Server 2025 improves monitoring and observability by expanding the available diagnostic tools and giving DBAs deeper visibility into system behavior. These enhancements cover new DMVs, richer Extended Events, improved Query Store integration, and updates to the Performance Dashboard in SSMS 20+. The goal is to detect performance problems earlier and diagnose them more accurately without relying on external tools.

8.1 New Dynamic Management Views (DMVs)

SQL Server 2025 introduces new DMVs and extends existing ones to support modern workloads such as AI operations, external REST calls, and advanced query processing. Key areas include:

AI Workload Monitoring

DMVs track embedding generation, external model execution, and resource usage when calling REST endpoints through sp_invoke_external_rest_endpoint.

Query Processing Feedback

New DMVs expose details about:

- - Cardinality Estimation Feedback (for expressions, skewed data, CASE statements, etc.).
  - Memory Grant Feedback (3rd generation).
  - Plan choice adjustments under IQP.

REST and External Operations

Additional logging and DMV entries support REST workloads including execution times, error codes, and retry logic.

These additions help DBAs understand query behavior, detect regressions, and optimize AI or external-service interactions.

Why It Matters for DBAs

Faster and more accurate troubleshooting.
Clear visibility into AI and REST workloads (which were previously difficult to monitor).
Better tuning decisions using runtime feedback data.

Test example:

-- Cardinality Estimation Feedback (new & enhanced)
SELECT database_id, fingerprint, feedback, observed_count, state
    FROM sys.dm_exec_ce_feedback_cache;

-- Memory Grant Feedback – queries that received adjustments
SELECT  session_id, requested_memory_kb, granted_memory_kb, used_memory_kb,
        is_feedback_available
    FROM sys.dm_exec_query_memory_grants
    WHERE is_feedback_available = 1;

(AI and REST-related DMVs vary by build; final documentation will provide complete names.)

8.2 Performance Dashboard Improvements

The Performance Dashboard in SSMS 20+ is optimized for SQL Server 2025. It now supports:

Real-time monitoring of vector and AI workloads.
Better visualization of wait statistics, memory consumption, and worker thread usage.
More accurate alerts for long-running queries and abnormal IO latency.

While not a full redesign, the updated dashboard is more responsive and aligned with modern workloads. Why It Matters for DBAs

Quick performance insights without third-party tools.
Useful for triage and early-stage diagnosis.
Supports new engine behaviors introduced in SQL Server 2025.

Test example:

To open the dashboard: SSMS → Object Explorer → Server → Reports → Standard Reports → Performance Dashboard

8.3 Advanced Extended Events (XE)

SQL Server 2025 enhances Extended Events with several new capabilities:

New Events for Modern Behavior
- Parameter sniffing details
- IQP feedback events
- DOP (parallelism) feedback
- Log flush delays
- External REST execution metadata
Time-Bound Extended Event Sessions

A major usability improvement: sessions can now include a MAX_DURATION setting that stops them automatically. This prevents forgotten sessions from consuming excessive storage or CPU. Why It Matters for DBAs

Safer diagnostics—no more huge XE files from forgotten sessions
More accurate troubleshooting for parallelism, cardinality issues, and query regressions
Better visibility into workloads that interact with external REST APIs

Test example:

-- Create a session that automatically stops after 10 minutes
CREATE EVENT SESSION [TimeBoundSession] ON SERVER 
    ADD EVENT sqlserver.sql_statement_completed(
        ACTION(sqlserver.sql_text))
    ADD TARGET package0.event_file(SET filename=N'C:\Temp\TimeBound.xel')
    WITH (MAX_DURATION = 10 MINUTES);

ALTER EVENT SESSION [TimeBoundSession] ON SERVER STATE = START;

9. Other Important Features for DBAs

SQL Server 2025 introduces several additional features that affect everyday database administration. These improvements enhance transaction management, external data access, and licensing flexibility. They make SQL Server more scalable, cost-effective, and easier to manage across different environments.

9.1 New Transaction Manager

The Transaction Manager has been enhanced with new Optimized Locking techniques, including TID Locking and Lock After Qualification (LAQ). These mechanisms reduce unnecessary lock contention by releasing locks earlier in query execution.Key benefits include:

Fewer random deadlocks
Smarter lock escalation
Better concurrency during high OLTP workloads
No code changes required
Requires Accelerated Database Recovery (ADR)

Why It Matters for DBAs

Reduced blocking and deadlocks
More predictable transaction behavior
Lower workload on DBAs for troubleshooting concurrency issues

Test example:

-- Enable Optimized Locking (ADR required)
ALTER DATABASE CURRENT SET ACCELERATED_DATABASE_RECOVERY = ON;
ALTER DATABASE SCOPED CONFIGURATION SET OPTIMIZED_LOCKING = ON;

-- Check locks
SELECT resource_type, request_mode, request_status, resource_description
    FROM sys.dm_tran_locks;

9.2 Improvements in PolyBase and External Data

PolyBase is now more stable and supports modern storage formats, including Parquet and Iceberg, for on-premises SQL Server. Connection reliability is improved with smarter retry logic, and Azure connections can use Managed Identity, reducing the need for shared keys or credentials.

Why It Matters for DBAs

Easier integration with data lakes (Fabric, Azure Data Lake Storage)
Ability to query external data without heavy ETL pipelines
More reliable performance in hybrid architectures

Test example:

-- Example: External table using Parquet
CREATE EXTERNAL DATA SOURCE AzureStorage
    WITH (
        LOCATION = 'abfss://container@storageaccount.dfs.core.windows.net',
        CREDENTIAL = NULL  -- Using Managed Identity
    );

CREATE EXTERNAL FILE FORMAT ParquetFormat WITH (FORMAT_TYPE = PARQUET);

CREATE EXTERNAL TABLE ExternalSales (
    SaleID INT, Amount DECIMAL(10,2)
)
WITH (
    LOCATION = '/sales/',
    DATA_SOURCE = AzureStorage,
    FILE_FORMAT = ParquetFormat
);

SELECT TOP 10 * 
    FROM ExternalSales;

9.3 Improvements in Editions and Licensing

SQL Server 2025 includes licensing and edition changes that directly influence cost and capacity planning:

Full Resource Governor in Standard Edition

(including tempdb governance)

Higher resource limits in Standard Edition

– up to 32 cores – up to 256 GB buffer pool

Express Edition increased to 50 GB per database
New Standard Developer Edition

Free for development and testing environments

Why It Matters for DBAs

Lower infrastructure and licensing costs
Better scalability for small and mid-sized environments
Reduced need to upgrade to Enterprise Edition prematurely

Test example:

-- Check edition and engine type
SELECT SERVERPROPERTY('Edition') AS Edition,
       SERVERPROPERTY('EngineEdition') AS EngineEdition;

-- Confirm Resource Governor
SELECT * 
    FROM sys.resource_governor_workload_groups;

Summary Table — SQL Server 2025 Key Enhancements

Category	Key Improvements	Practical Impact for DBAs
Security & Encryption	Always Encrypted v2, Secure Enclaves GA, TDS 2.0 enforcement	Stronger data protection, reduced attack surface, encrypted query execution without exposing data
Intelligent Query Processing (IQP)	Adaptive plans (vNext), Memory Grant Feedback 3.0, CE 3.0, Optional Parameter Plan Optimization (OPPO), Smart parallelism (DOP Feedback)	More stable plans, fewer spills, reduced parameter sniffing, improved performance without code changes
TempDB & Storage	TempDB Space Governance, improved allocation (PFS/GAM/SGAM), ADR in tempdb, tmpfs on Linux	Reduced contention, fewer outages, faster tempdb operations, improved concurrency
Backup & Restore	Backups on secondary replicas, ZSTD compression, immutable Azure backups, Managed Identity authentication	Faster backups, lower storage cost, ransomware protection, no credential management
Automation & Governance	Updated System Insights, deeper Azure Arc/Fabric integration, improved Query Store regressions	Better predictive analytics, easier governance, more proactive tuning
Memory/CPU/IO Management	Better buffer pool eviction, improved I/O analytics via DMVs, smarter concurrency management	Lower latency, fewer PAGEIOLATCH waits, better stability under high load
High Availability & DR	Faster failover, better sync commit, Query Store on secondaries, distributed AG improvements, ADR expansion	Reduced RTO/RPO, better read-scale, more reliable multi-site HA
Fabric Lakehouse Mirroring	Zero-ETL mirroring to Fabric/OneLake	Real-time analytics without ETL overhead
PolyBase & External Data	Better reliability, Parquet & Iceberg support, Managed Identity for external sources	Easier integration with data lakes and hybrid architectures
Edition & Licensing	Resource Governor in Standard, higher limits, 50 GB Express, new Standard Developer Edition	Lower licensing cost and higher scalability

Conclusion

SQL Server 2025 delivers a major step forward, with improvements across security, performance, HA/DR, AI integration, and monitoring. Features such as ZSTD backups, advanced IQP, updated Availability Groups, stronger observability, and optimizations in transaction management all contribute to a more stable and scalable platform. For DBAs, SQL Server 2025 provides a modern, AI-aware environment that reduces manual effort and supports enterprise workloads more efficiently than previous releases. We strongly recommend testing new features in a development or staging environment before full deployment, ideally with compatibility level 170 to ensure maximum benefit.

SQL Server 2025 Upgrade Checklist

Pre-Upgrade Preparation

- Verify hardware and OS compatibility (Windows Server 2025 or supported Linux distributions).
- Update firmware, BIOS, NIC drivers, and storage drivers.
- Check .NET Framework and PowerShell versions (if required by tooling).
- Validate antivirus exclusions for SQL binaries, data/log, and tempdb.

Database & Instance Preparation

- Perform full backups of system + user databases.
- Run DBCC CHECKDB on all databases.
- Ensure no active corruption and no long-running transactions.
- Confirm free space: at least 2× size of the biggest database on the target drive.
- Export SQL Agent jobs, operators, alerts, and SSIS packages.
- Export Resource Governor and policy configurations (if used).

Performance & Compatibility Prep

- Record baseline: waits, CPU load, memory usage, top 20 queries, index stats.
- Enable Query Store on all databases before upgrade.
- Set databases temporarily to compatibility level 160 before upgrade (recommended).
- Validate unsupported features (e.g., deprecated syntax, removed components).

In-Place Upgrade / Migration

- Confirm all logins, certificates, and linked servers are scripted.
- Validate encryption keys and TDE certificates (mandatory for restore).
- If AGs exist, review read/write routing and failover policies.
- For Linux: confirm correct file permissions and mount points (tmpfs optional for tempdb).

Post-Upgrade Configuration

- Set all databases to compatibility level 170.
- Enable:
  - Intelligent Query Processing (IQP)
  - Optimized Locking
  - ZSTD compression (optional)
  - ADR (required for optimized locking)
  - Query Store on secondaries (AG)
  - TempDB Space Governance (Standard/Enterprise)
- Update statistics with FULLSCAN.
- Rebuild fragmented indexes.
- Review memory grant feedback and CE feedback DMVs.

Validation & Monitoring

Monitor:
- dm_exec_query_stats
- dm_os_wait_stats
- dm_io_virtual_file_stats
- dm_exec_ce_feedback_cache
Check for plan regressions in Query Store.
Validate backup/restore performance with ZSTD and secondary backups.
Enable new Extended Events sessions (especially for parameter sniffing and DOP feedback).

Optional: Cloud/Fabric Integration

- Configure backup to URL with Managed Identity.
- Test immutable backups for ransomware protection.
- Enable Fabric mirroring for real-time analytics (optional).

New Features in SQL Server 2025 for DBAs

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Pre-Upgrade Preparation

Database & Instance Preparation

Performance & Compatibility Prep

In-Place Upgrade / Migration

Post-Upgrade Configuration

Validation & Monitoring

Optional: Cloud/Fabric Integration

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