SQL Server 2025 RC0: Ubuntu 24.04 support and TLS 1.3 by default

Microsoft has pushed the first public Release Candidate (RC0) of SQL Server 2025 into preview with two headline changes that matter to every Windows-centric IT team experimenting with Linux-first development: official Ubuntu 24.04 support for dev/test scenarios and TLS 1.3 enabled by default, with container-ready artifacts and quickstart guidance to make testing painless.

Background​

Microsoft’s SQL Server on Linux initiative has steadily broadened platform support and hardened security since the first Linux release. The SQL Server 2025 RC0 preview represents the next step in that evolution by aligning with the newest Ubuntu LTS and with modern transport security standards. For organizations that balance Windows server infrastructure with Linux-based developer tooling, this preview reduces friction for developing and validating Linux-hosted SQL Server scenarios while also bringing default secure-by-design behavior to connections.
Microsoft’s official guidance frames the RC0 offering as a dev/test convenience: the release ships as an Enterprise Evaluation Edition valid for 180 days, intended for experimentation and validation rather than immediate migration of production workloads. The company explicitly recommends continuing to run mission-critical systems on SQL Server 2022 on supported Linux platforms such as Ubuntu 22.04 or RHEL 9 until broader certification and GA-level support arrive. (techcommunity.microsoft.com, neowin.net)

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What’s new, at a glance​

• Ubuntu 24.04 support for SQL Server 2025 RC0 in dev/test scenarios, with a 180-day Enterprise Evaluation image available.
• TLS 1.3 enabled by default, paired with TDS 8.0 changes that shift the connection sequence to enforce encryption earlier in the handshake.
• Container images and quickstarts for rapid local testing (including guidance for WSL2 + Docker Desktop).
• Continued production recommendation: remain on SQL Server 2022 for critical workloads until Ubuntu 24.04 certification and full GA stability are confirmed. (techcommunity.microsoft.com, neowin.net)

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Ubuntu 24.04: why this matters​

A new LTS in the ecosystem​

Ubuntu 24.04 is the latest Long-Term Support release from Canonical and will be the platform of choice for many cloud and developer desktops over the coming years. Native support for a new LTS matters to enterprises that standardize images across development, CI, and production platforms. By providing an evaluation channel for Ubuntu 24.04, Microsoft shortens the feedback loop between Linux-based environments and SQL Server engineering teams.

Dev/test vs production: clear boundaries​

The preview’s Enterprise Evaluation license is explicitly time-limited (180 days). Microsoft’s documentation makes the distinction clear: the RC0 image is suitable for development and testing but not recommended for production. For organizations that manage compliance and SLAs, this is an important guardrail—testing on 24.04 is now feasible, but migration requires certification and verified operational stability.

What administrators should check when validating Ubuntu 24.04​

When testing SQL Server 2025 on Ubuntu 24.04, teams should validate:

• Kernel compatibility and host kernel version for container hosts.
• Docker/OCI runtime compatibility and storage drivers used in test environments.
• Backup and restore flows between Ubuntu 22.04 production images and Ubuntu 24.04 test images.
• Performance baselines—IO, memory use, and CPU profiles—compared to SQL Server 2022 instances.
• Integration with monitoring, observability, and security tooling (e.g., audit logs, agent-based monitoring).

A test matrix that covers these items will help teams judge whether to move to a staged certification path or remain with the currently supported production stack. (forums.docker.com, techcommunity.microsoft.com)

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TLS 1.3 by default: the technical impact​

What changed in the connection model​

SQL Server 2025 introduces broader adoption of TDS 8.0 and enables TLS 1.3 out of the box for RC0. The combined effect is a security posture shift: the prelogin and authentication phases can now be encrypted earlier, and TLS 1.3’s streamlined handshake reduces latency and removes legacy cryptographic constructs. The new connection sequence shifts to:
TCP handshake → TLS handshake → TDS prelogin (encrypted) → Authentication (encrypted) → Data exchange (encrypted)
This order reduces the attack surface during initial negotiation and enforces encryption semantics from the start of the connection.

Benefits of TLS 1.3 default enablement​

• Faster handshakes through reduced round-trips versus legacy TLS versions, producing measurable improvements in connection latency for high-churn workloads.
• Stronger, modern ciphers and removal of deprecated algorithms—reducing risk from protocol-level weaknesses.
• Compliance alignment with up-to-date security standards favored by regulated industries and security frameworks.

Caveats and compatibility considerations​

Although TLS 1.3 is a best-practice move, some legacy clients, drivers, or middleboxes may not fully support TLS 1.3 or TDS 8.0 semantics. Organizations should:

• Test client drivers (.NET, JDBC, ODBC) used by applications to confirm TLS 1.3 negotiation and cipher compatibility.
• Validate any connection-proxying devices or appliances (e.g., load balancers, TLS terminators, middleboxes) for TLS 1.3 support.
• Evaluate telemetry and observability tools for visibility into TLS 1.3 sessions (some older tools have limited visibility into TLS 1.3 internals).

Microsoft’s guidance includes updated Learn content and verification steps for encrypted connections. Teams should adopt a test-and-rollback plan for environments where legacy client compatibility is uncertain.

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Container-first testing made simple​

Quickstart and Docker image​

Microsoft published an MCR container image for the RC0 preview—developers can pull the tagged artifact and run it with a couple of Docker commands. The published snippet demonstrates how to pull and run the image for local dev/test scenarios, including WSL2 integration on Windows developer machines. This makes it trivial to validate SQL Server 2025 behavior without changing host OS installations.
Example (as shown in the official quickstart):

• docker pull mcr.microsoft.com/mssql/server:2025-RC0-ubuntu-24.04
• docker run -e "ACCEPT_EULA=Y" -e "MSSQL_SA_PASSWORD=<password>" -e "MSSQL_AGENT_ENABLED=true" -p 14333:1433 --name sql2025preview -d mcr.microsoft.com/mssql/server:2025-RC0-ubuntu-24.04

The container-based path is particularly attractive for CI pipelines and ephemeral test environments, where teams can script validation scenarios and tear down images at the end of test runs.

WSL2 as a dev platform​

Running the preview inside WSL2 + Docker Desktop provides Windows developers the convenience of Linux-native images without separate Linux hosts. Microsoft’s demos show connecting from SQL Server Management Studio (SSMS) on Windows to the containerized instance running in WSL2, with the ERRORLOG used to confirm the SQL Server version and runtime environment. This lowers the barrier for Windows-first teams to validate Linux deployment behaviors.

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Broader SQL Server 2025 feature context​

SQL Server 2025 is shaping up to be a platform-focused release with multiple advances beyond OS support and transport security. Announcements and reporting on preview releases highlight features such as:

• AI-integrated database capabilities (vector embeddings and native support in drivers), intended to accelerate AI workloads that require high-throughput embedding storage and retrieval. (neowin.net, techcommunity.microsoft.com)
• Performance improvements in drivers (claims of significantly faster reads, writes, and bulk copy operations for certain scenarios in the preview testing). These claims should be validated against real workloads—synthetic benchmarks and microbenchmarks can exaggerate gains versus complex production schemas.
• Encryption enhancements such as OAEP-256 support for RSA-based encryption conditioned on database compatibility level, presenting stronger key protection options for workloads requiring higher cryptographic assurances.

These features illustrate Microsoft’s dual emphasis on modern application patterns (AI and vector workloads) and security modernization (encryption defaults and algorithm upgrades). However, each new capability also increases the testing surface for compatibility, monitoring, and operational practices.

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Migration and upgrade considerations​

Risk matrix for moving from 2022 to 2025 (preview → GA)​

• Compatibility risk: Database compatibility levels, T-SQL behavior changes, and new encryption defaults can impact applications that assume prior behaviors.
• Operational maturity: Full support for Availability Groups, Failover Clusters, and other HA features may lag initial previews and need verification.
• Driver and client compatibility: Driver versions must support TDS 8.0 and TLS 1.3; older drivers may require updates or configuration changes.
• Third-party ecosystem: Backup vendors, monitoring tools, and security appliances must be tested for compatibility with the new transport and cryptographic defaults.
• Certification and support: Production migration should wait for Microsoft’s certification of Ubuntu 24.04 and clear GA timelines.

Practical upgrade path (recommended)​

• Keep production on SQL Server 2022 or another fully supported configuration until certification is confirmed.
• Establish a parallel test farm running SQL Server 2025 RC0 on Ubuntu 24.04 to validate application behavior, driver compatibility, and operational workflows.
• Use containerized deployments and WSL2 for developer validation and performance baselines to model expected production behavior.
• Maintain a rollback plan that includes data restore tests from backups taken from the 2025 test environment to the production 2022 environment to verify backward compatibility.
• Monitor Microsoft’s release notes and community feedback channels for bug reports, hotfixes, and certification announcements. (techcommunity.microsoft.com, neowin.net)

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Security analysis: gains and potential blind spots​

Strengths​

• Default TLS 1.3 dramatically reduces the likelihood of weak-cipher negotiation and improves resilience against a variety of network-layer attacks. This is a major step forward for “secure by default” posture.
• TDS 8.0 encryption enforcement for the prelogin and authentication phases means sensitive negotiation data is no longer transmitted in cleartext or under weaker protection.
• Modernized cryptographic defaults (e.g., OAEP-256) give teams stronger primitives for encrypting data-at-rest keys and certificates.

Risks and operational considerations​

• Compatibility gaps with legacy clients are the most immediate operational risk. If internal applications use older drivers or embedded connection libraries that cannot negotiate TLS 1.3 or TDS 8.0, connection failures or degraded fallbacks may occur.
• Visibility limitations: Some monitoring tools that inspect TLS handshakes or terminate TLS for inspection may not yet fully support TLS 1.3 semantics. Observability and traffic analysis workflows must be validated.
• Misconfiguration risk: Administrators unfamiliar with TLS 1.3 or new cipher defaults may inadvertently weaken security by misconfiguring custom cipher suites or fallback behaviors. Proper governance and configuration templates are recommended.
• Certification lag: Until Ubuntu 24.04 and SQL Server 2025 reach GA-level certifications, organizations reliant on compliance certifications should avoid production migration.

Overall, the security changes are favorable and align with industry guidance, but they require disciplined testing, driver updates, and configuration management to avoid operational disruptions.

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Quickstart: recommended test plan (developer-friendly)​

• Prepare a Windows dev box with WSL2 and Ubuntu 24.04 installed, or a Linux VM running Ubuntu 24.04.
• Pull the RC0 container image:
• docker pull mcr.microsoft.com/mssql/server:2025-RC0-ubuntu-24.04.
• Launch the container with a secure SA password and appropriate port mapping.
• Connect with SSMS, sqlcmd, or your application driver and inspect ERRORLOG to validate version and runtime environment.
• Validate TLS 1.3 negotiation by:
• Forcing client connection logs to show TLS version, or
• Using packet capture tools that can identify TLS version or using server-side logs that show negotiated TLS versions.
• Run schema compatibility tests, stored procedure execution, and performance microbenchmarks that reflect production workloads.
• Test backups and restores between the test instance and a production-like SQL Server 2022 instance to verify portability.
• Iterate on driver updates and connection strings if any compatibility or negotiation issues appear.

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Community feedback and real-world early reports​

The early public discussion shows both excitement and cautious testing. Outlets and community threads report that while many developers can run the RC0 container successfully on WSL2, there are also kernel and runtime edge cases reported in broader container forums that administrators should watch. These community conversations will be important to monitor as more users validate networking, kernel interactions, and storage semantics on Ubuntu 24.04 hosts. (forums.docker.com, neowin.net)

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Recommendations for IT teams and DBAs​

• Use RC0 to validate application behavior, driver compatibility, and operational runbooks in a controlled dev/test environment.
• Delay production migrations until Microsoft formally certifies Ubuntu 24.04 and until high-availability and backup vendors confirm support for SQL Server 2025 GA. (techcommunity.microsoft.com, neowin.net)
• Prioritize driver upgrades and test TLS 1.3 negotiation paths for all application stacks—this is the single biggest compatibility area to validate.
• Integrate TLS 1.3 observability checks into your monitoring and incident playbooks to ensure you can detect connection-level anomalies post-migration.
• Leverage containers and WSL2 for rapid iteration—script your tests to make results reproducible across teams.

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Final assessment​

SQL Server 2025 RC0’s support for Ubuntu 24.04 and TLS 1.3 enabled by default are meaningful steps that bring modern platform alignment and stronger transport security to the SQL Server ecosystem. For developers and organizations building Linux-first or hybrid systems, the preview lowers the barrier to testing and validation, particularly thanks to container images and WSL2 guidance.
At the same time, the preview is deliberately scoped for dev/test and carries attendant caveats: production workloads should remain on certified, supported builds (such as SQL Server 2022 on Ubuntu 22.04) until Microsoft issues GA certifications and ecosystem vendors confirm support. The TLS 1.3 shift is a robust security win, but driver, client, and monitoring compatibility must be validated to avoid unexpected disruptions.
For Windows-first teams that want to embrace Linux-hosted databases without committing production resources, this RC0 makes sensible exploration straightforward. For operations and compliance teams, the prudent route is a staged validation program that combines containerized testing, driver compatibility checks, and an explicit rollback plan until GA and certification follow. (techcommunity.microsoft.com, neowin.net)
The SQL Server 2025 preview signals a forward-looking platform posture—closer integration with modern Linux LTS releases and a decisive move to secure-by-default transports. The next steps for teams are practical: test broadly, measure carefully, and wait for certification before rewriting production runbooks.

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Source: Windows Report Microsoft Previews SQL Server 2025 with Ubuntu 24.04 and TLS 1.3

 

[ChatGPT]

Microsoft’s Release Candidate 0 for SQL Server 2025 marks a decisive step toward a modern, AI‑first database platform — with official Ubuntu 24.04 support for development and testing, TLS 1.3 enabled by default, and a broad slate of performance and AI features that aim to reshape how enterprises build next‑generation applications.

Overview​

The RC0 preview of SQL Server 2025 is explicitly targeted at development and validation workflows rather than immediate production migrations. Microsoft has published container images and quickstart guidance to make evaluation straightforward, and the RC0 artifacts ship as an Enterprise Evaluation Edition that expires after 180 days. The preview introduces two headline changes that will be most visible to infrastructure and security teams: official Ubuntu 24.04 support for dev/test scenarios and TLS 1.3 enabled by default. Beyond those platform changes, SQL Server 2025 RC0 expands the engine’s AI and developer toolkit with native vector/embedding support, driver optimizations, JSON and REST enhancements, and concurrency improvements designed to reduce lock memory consumption and blocking under heavy transactional load.
This feature set signals Microsoft’s intent to deliver a database engine that is not only modern in transport security and Linux platform alignment but explicitly engineered for AI workloads and the operational realities of cloud‑native development.

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Background: why this release matters​

SQL Server’s evolution onto Linux over recent years opened the product to hybrid stacks and containerized development pipelines. Supporting the latest Ubuntu LTS releases matters because enterprises often standardize developer images, CI runners, and cloud VM images on LTS kernels. By providing an RC0 build that runs on Ubuntu 24.04, Microsoft shortens the feedback loop for organizations preparing to adopt the new Ubuntu baseline.
At the same time, enabling TLS 1.3 by default reflects a larger industry shift toward secure‑by‑default configurations. For organizations managing regulated data or strict compliance regimes, transport security defaults can simplify governance and reduce the risk of misconfiguration.
Finally, embedding vector support and accelerating drivers signals that Microsoft sees SQL Server not merely as a row-store but as a platform for operational AI: vector similarity, retrieval‑augmented generation (RAG) patterns, and tight application‑driver integration.

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What’s new in RC0 — the feature map​

• Ubuntu 24.04 support (dev/test only) — Enterprise Evaluation Edition image available for 180 days.
• TLS 1.3 enabled by default, with a TDS connection model that enforces encryption earlier in the handshake.
• Built‑in vector/embedding support and driver optimizations in .NET and JDBC intended to accelerate AI workloads.
• Driver performance claims for specific vector and bulk operations (read/write/bulk improvements in preview).
• Copilot integration in SQL Server Management Studio (SSMS) to assist development and management tasks.
• Native JSON support and other developer‑oriented features.
• Optimized Locking with Transaction ID Locking and Lock After Qualification to reduce lock memory usage and minimize blocking.

Each of these items changes how database teams will validate, test, and eventually adopt SQL Server 2025.

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Ubuntu 24.04: dev/test support and practical implications​

Why Ubuntu 24.04 support matters​

Ubuntu 24.04 is the latest Long‑Term Support (LTS) release in the Ubuntu cadence. For organizations that standardize on a single LTS across developer workstations, CI/CD runners, and cloud VM images, having a SQL Server preview that runs natively on 24.04 lets teams validate images and deployment scripts ahead of a full OS refresh.

Guardrails and licensing​

The RC0 image is distributed as an Enterprise Evaluation Edition and is explicitly time‑limited to 180 days. Microsoft’s guidance positions this build for experimentation, validation, and early compatibility testing rather than for production workloads. Organizations should treat the RC0 as a staging channel — useful for functional validation, driver testing, and performance baselining, but not for SLA‑backed services or regulated production data.

What to validate when testing on 24.04​

When teams spin up RC0 containers or VMs on Ubuntu 24.04, the following validation checklist will reduce migration risk:

• Kernel compatibility and host kernel version for containerized hosts.
• Docker/OCI runtime and storage driver behavior under typical workload patterns.
• Backup and restore interoperability with SQL Server 2022 (especially when moving data between 22.04 and 24.04 test images).
• Performance baselines for IO, memory, and CPU compared to representative SQL Server 2022 instances.
• Observability and monitoring integrations — ensure agents, audit logs, and telemetry tools work as expected.
• High‑availability and disaster recovery paths — do failover/replica workflows behave as intended in test environments?

A disciplined test matrix will reveal whether an organization can confidently move forward when GA certifications and ecosystem vendor support arrive.

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TLS 1.3 and the new connection model: technical impact​

What changed​

SQL Server 2025 RC0 adopts TLS 1.3 by default and moves toward a TDS (Tabular Data Stream) model that emphasizes earlier encryption of the connection sequence. The revised order for connection negotiation becomes:

• TCP handshake
• TLS handshake (TLS 1.3 by default)
• TDS prelogin (encrypted)
• Authentication (encrypted)
• Data exchange (encrypted)

This change ensures encryption is in place earlier in the life of each connection and removes legacy cipher choices and handshake steps that were part of older TLS versions.

Benefits​

• Faster handshakes: TLS 1.3 reduces round trips vs older TLS versions, which lowers latency for high‑churn connection patterns.
• Stronger cryptography: TLS 1.3 deprecates legacy ciphers and favors modern, secure primitives.
• Reduced exposure window: encrypting the prelogin and authentication phases reduces the amount of unprotected negotiation metadata on the wire.
• Compliance alignment: many regulatory frameworks and auditors prefer TLS 1.3 as a minimum for modern deployments.

Operational caveats​

• Legacy client compatibility: older drivers, embedded libraries, or intermediate TLS‑terminating middleboxes may not support TLS 1.3 or may interact poorly with the changed TDS sequence. Validation of .NET, JDBC, and ODBC drivers is essential.
• Observability concerns: some packet‑inspection or TLS‑terminating monitoring tools rely on older TLS semantics and may need updates to fully support TLS 1.3 visibility.
• Misconfiguration risk: administrators unfamiliar with TLS 1.3 cipher defaults or with TDS 8.0 semantics can inadvertently weaken posture if they create unsafe custom fallbacks. Follow secure configuration templates and avoid ad‑hoc cipher overrides.

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Vector embeddings, driver optimizations, and performance claims​

What’s being introduced​

SQL Server 2025 RC0 includes built‑in vector embedding support and driver‑level optimizations in the .NET and JDBC clients. These changes are targeted at AI and search workloads where fast similarity search and high‑throughput reads/writes of vector data are paramount.
Microsoft’s preview reporting highlights substantial performance improvements in specific scenarios:

• Read operations reported to be up to 50× faster in particular vector retrieval workloads.
• Write operations described as more than 3× faster in certain conditions.
• Bulk copy operations claimed to be approximately 19× faster for the previewed paths.

How to interpret the numbers​

Those figures reflect preview measurements and driver‑level optimizations for targeted vector workflows. While impressive on paper, they should be interpreted cautiously:

• These are likely derived from microbenchmarks or carefully controlled test harnesses that focus on vector‑centric workloads, not broad OLTP or mixed transactional workloads.
• Real applications with complex schemas, joins, and multi‑tenant behavior will see different gains. Synthetic benchmarks often exaggerate potential performance uplift.
• Gains will vary depending on hardware (CPU, memory, NVMe), storage stack, and the specifics of the vector index used.

Teams should run representative benchmarks that mirror production patterns before assuming these headline gains will materialize in live systems.

Why this matters for AI applications​

If the driver and engine improvements deliver consistent low‑latency vector retrievals and efficient bulk ingest, SQL Server positions itself as a credible platform for operational AI scenarios:

• Retrieval‑augmented generation (RAG) pipelines that require fast vector lookup near application latency budgets.
• In‑database vector stores for search, recommendations, and similarity matching.
• Consolidation of OLTP and vector workloads where proximity of relational and vector data reduces data movement and latency.

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Developer experience: Copilot, JSON, and integration​

Copilot in SSMS​

The RC0 preview includes Copilot integration in SQL Server Management Studio (SSMS) to help accelerate development and management tasks. Copilot is positioned to assist with query writing, schema exploration, and routine DBA tasks, reducing friction for developers who want contextual help inside the traditional management console.

Native JSON and developer APIs​

SQL Server 2025 introduces native JSON support, making it easier to model semi‑structured data without external libraries or heavy T‑SQL glue. Combined with REST/GraphQL patterns emerging elsewhere in the platform, this reduces impedance between modern application stacks and the database.

Quickstart for Windows developers​

Microsoft published a quickstart for running RC0 images inside WSL2 containers, enabling Windows‑first developers to test Linux‑native behavior without separate Linux hosts. A couple of Docker commands will spin up a containerized SQL Server 2025 RC0 that SSMS can connect to from the host.
Example quickstart flow:

• Pull the RC0 container:
  docker pull mcr.microsoft.com/mssql/server:2025-RC0-ubuntu-24.04
• Run the container (example):
  docker run -e "ACCEPT_EULA=Y" -e "MSSQL_SA_PASSWORD=<YourStrong!Passw0rd>" -p 14333:1433 --name sql2025preview -d mcr.microsoft.com/mssql/server:2025-RC0-ubuntu-24.04
• Connect with SSMS, sqlcmd, or application drivers and verify the ERRORLOG for the SQL Server version.

This containerized path is ideal for CI/CD pipelines, ephemeral test runners, and Windows developers who want to validate Linux deployment behavior without multi‑host complexity.

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Concurrency and locking: Optimized Locking, TID Locking, and LAQ​

What Optimized Locking changes​

SQL Server 2025 RC0 introduces an Optimized Locking mechanism designed to reduce lock memory consumption and minimize blocking. The preview highlights two techniques:

• Transaction ID (TID) Locking — a finer‑grained approach that ties locks more directly to transaction identifiers to reduce lock object memory and improve contention handling.
• Lock After Qualification (LAQ) — deferment of certain locks until after qualification phases, which can decrease blocking windows for read‑heavy or concurrent transactional workloads.

Practical impact​

For high‑concurrency OLTP systems, reducing lock memory and minimizing blocking can substantially improve throughput and reduce latency under contention. However:

• These are low‑level concurrency semantics changes and require careful compatibility testing. Behavior of stored procedures, isolation levels, and existing concurrency‑reliant application logic should be validated.
• Changes might affect diagnostic tooling and lock monitoring dashboards; observability investments must be updated to interpret the new locking models.

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Migration guidance and risk matrix​

Recommended posture​

• Keep production workloads on SQL Server 2022 and supported Linux distros (e.g., Ubuntu 22.04, RHEL 9) until SQL Server 2025 reaches GA and ecosystem vendors certify compatibility.
• Use RC0 for:
• Driver and application compatibility testing.
• Functional validation of new features (vectors, JSON, Copilot workflows).
• Performance baselining with representative workloads.
• Maintain a rollback strategy that includes restore and compatibility checks between 2022 and 2025 environments.

Key risk areas to validate​

• Driver compatibility: Ensure .NET, JDBC, and ODBC drivers in use can negotiate TLS 1.3 and TDS 8.0 semantics.
• Middlebox and load balancer behavior: TLS termination and proxy devices must be validated for TLS 1.3.
• Backup/restore and HA: Validate backup portability between 2022 and 2025 test builds and confirm Availability Group behavior (some HA features may be updated post‑GA).
• Third‑party tooling: Confirm that backup vendors, monitoring platforms, and security appliances support the new defaults and protocols.
• Compliance and certification: Organizations with strict regulatory or certification needs should await GA and vendor attestations before moving production data.

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Practical checklist for testing RC0 in your environment​

• Prepare a dedicated dev/test project and label it clearly as RC0 evaluation.
• Establish a reproducible test harness: scripted Docker/WSL2 deployments and teardown.
• Run a compatibility sweep:
• Connect using current .NET, JDBC, ODBC drivers; test authentication and TLS negotiation.
• Execute stored procedures, triggers, and scheduled jobs to check behavior.
• Validate transport security:
• Confirm TLS 1.3 negotiation in client connection logs or packet captures.
• Verify monitoring and inspection tools can observe connections or are updated for TLS 1.3.
• Perform functional tests:
• Vector insert/read workloads and compare latencies to 2022 baselines.
• Bulk copy and data ingestion pipelines to validate performance claims against real data shapes.
• Simulate failover and backup restores to ensure DR procedures work between 2022 and 2025 environments.
• Audit and telemetry:
• Ensure audit logs, query store, and performance counters remain comprehensive and intelligible under the new locking semantics.
• Record and report issues: maintain a list of incompatibilities to share with vendors and product engineering.

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Strengths and strategic opportunities​

• Modern transport security: Enabling TLS 1.3 by default is a meaningful security posture improvement and reduces the cognitive load for secure configuration.
• Linux alignment: Official Ubuntu 24.04 support—even as an evaluation release—lowers friction for teams standardizing on the newest LTS for development and CI.
• AI and vector readiness: Native vector support plus driver optimizations position SQL Server as a serious platform for operational AI workloads, and may simplify architectures that otherwise require separate vector stores.
• Developer ergonomics: Copilot in SSMS and native JSON support shrink the gap between developer expectations and database ergonomics, speeding iteration.

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Risks, unknowns, and things to watch​

• Preview performance claims need real‑world validation. Headline numbers for reads/writes/bulk are promising but were measured in preview contexts; synthetic benchmarks can overstate gains for complex production workloads.
• Compatibility with legacy clients and appliances. TLS 1.3 and TDS 8.0 semantics will uncover edge cases in older drivers, connection pools, and TLS‑intercepting devices.
• Certification lag: Until GA and ecosystem vendors update their support matrices (backup solutions, HA tools, observability suites), production migrations are premature.
• Operational learning curve: New locking semantics and crypto defaults require DBAs and security teams to update playbooks and monitoring thresholds.
• Feature parity for HA and ecosystem tooling: Some high‑availability features and integrations may not be fully updated in RC0 and will arrive later in the GA cadence.

Where claims could not be independently verified (for instance, exact benchmark methodologies used for driver performance figures), treat them as vendor‑reported preview numbers and subject them to your own testing regimen.

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Bottom line: what DBAs and Windows teams should do now​

• Treat SQL Server 2025 RC0 as a testing and validation opportunity, not a production target.
• Start a controlled proof‑of‑concept project that evaluates:
• TLS 1.3 negotiation across your client stacks and middleboxes.
• Vector workload performance using representative data and index settings.
• Backup/restore and HA workflows between SQL Server 2022 and RC0 images.
• Use containers and WSL2 to speed iteration and keep test environments reproducible.
• Maintain communication with third‑party vendors (backup vendors, monitoring tool vendors, load‑balancer providers) to learn their timelines for 2025 compatibility.
• Document and automate your findings so that, when GA arrives, you can move from validation to a staged, well‑tested production adoption plan.

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Final assessment​

SQL Server 2025 RC0 draws a clear roadmap: modern Linux support, secure‑by‑default transports, and an engine optimized for AI and vector workloads. For Windows‑centric organizations that also operate Linux‑centric development pipelines, the RC0 preview provides an accessible, containerized path to validate future production configurations.
The release is strategically sensible — provide early access for developers and QA teams while keeping production recommendations conservative. The most compelling changes (TLS 1.3 default, vector embedding support, driver optimizations, and optimized locking) each address real operational and architectural needs for modern applications. However, the preview’s performance claims and low‑level concurrency changes demand careful, representative testing before any migration decision.
For DBAs, security teams, and architects, the immediate work is practical: validate drivers and middleboxes for TLS 1.3 and TDS 8.0, run representative vector and bulk workloads against RC0 containers, and update playbooks to reflect new encryption and locking defaults. Organizations that invest now in repeatable testing will be best positioned to reap the benefits of SQL Server 2025 once GA and ecosystem certifications arrive.

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Source: Techzine Global Microsoft SQL Server 2025 RC0 comes with Ubuntu 24.04 support