Reducing Application Downtime During SAP Sybase ASE Migration

Today, applications need to be available, responsive, and reliable to assist with everyday business operations to ensure they are performing. Many vital business processes rely on databases that work in the background, from financial transactions to managing inventory to customer relationship management and enterprise reporting. Productivity, customer satisfaction and revenue can be impacted if these databases need to be migrated and there is an interruption of any length.

SAP Sybase Adaptive Server Enterprise (ASE) is a relational database management system for transaction intensive enterprise applications. Organizations might think about moving or upgrading their ASE infrastructure to achieve greater infrastructure compatibility, better operational resilience, modern database administration, or to ensure technology matches evolving business needs. But it's not just about moving data when migrating an existing database environment. The applications, integrations, security configurations, stored procedures and processes will need to continue to function properly after the transition.

Understanding the Challenges of SAP Sybase ASE Migration

There are a number of technical and operational challenges to consider when migrating to a database. The complexity varies according to various factors such as source and target environments, size of the databases, application architecture, number of transactions, type of migration, etc.

Application Compatibility Challenges

There is one big issue to be considered: application compatibility. Specific SQL syntax, stored procedures, triggers, database drivers, transaction behavior, or configuration settings of ASE may be used by enterprise applications. Any change in these items in a migration can lead to unsuspected problems, even if the data has successfully moved.

Maintaining Data Consistency

Another major factor to take into account is data consistency. The migration process can continue to generate transactions at the same time that applications are being applied. Otherwise, the target environment may not have the proper information or it may have out-of-date information.

Infrastructure and Performance Differences

There might also be disparities in infrastructure which can impact performance. The performance of the application following the migration may vary because of changes in storage systems, memory allocation, CPU capacity, network latency, database configuration and indexing.

Common Operational Migration Challenges

Other typical challenges are:

• Discovering unknown application dependencies.
• Collaborating between the database and application teams.
• Handling a significant amount of data in a limited maintenance period.
• Validating transactions and business transactions.
• Preparing for transition back to home, if needed.
• Notifying business stakeholders of service outages.

Once these risks are understood early, organizations can put together a migration plan that is driven by measurable requirements, instead of assumptions.

1) Conduct a Comprehensive Pre-Migration Assessment

The first and most important step in a successful migration is to understand the current database environment. Organizations need to document the current support of the ASE system to their business operations before data move or infrastructure changes.

Document the Existing Database Environment

Database versions and sizes, volumes of transactions, periods of peak use, scheduled jobs, replication requirements, backup and recovery requirements are the first things that need to be determined. Examine objects in the database such as views, indexes, user defined functions, stored procedures, triggers, and tables.

Identify Application Dependencies

Dependencies of applications are equally important. List all applications, reporting tools, integrations, batch processes, and external applications that are connected to the database. Document connection strings, database drivers, authentication, network needs, and reliance on particular database actions.

Establish Performance Baselines

Performance baselines are also useful. Test transactions, queries, CPU usage, memory usage, storage latency and connections under normal and peak loads. These measurements will be used to compare with the target environment following migration.

2) Select the Right Migration Strategy

Migration method directly affects availability of the application. Organizations need to select an approach that best aligns with their technical requirements, volume of data, and business continuity needs.

Offline Migration

An offline migration is a process that temporarily disables any writes to the application, copies the necessary data and database objects to the target environment, validates the target environment, and then re-enables the application to write in the target environment.

The drawback is that the source database does not change in the final transfer, making this method relatively easy to do—and thereby making consistency management easier. If the database is large or the validation process is lengthy, however, then the downtime can be significant.

Online or Replication-Assisted Migration

If supported by the source and target architectures, an online migration approach can achieve minimal downtime by migrating an initial copy of data from the source system while it continues to operate. All changes are recorded and applied to the target until the target is sufficiently in sync with the source for a cutover.

Change capture can employ various tools and architectures such as transaction logs, replication technology or other supported change synchronization technologies.

This can help shorten the time in an outage, but adds complexity. Before production use, the following need to be addressed: replication lag, unsupported objects, transaction ordering, schema differences, and error handling.

Phased Migration

A phased migration is the gradual migration of applications, databases, or workloads in a carefully controlled group. It can minimise the risk of making one big move at a time, and provide teams with the opportunity to learn from previous migration stages.

But, in a phased migration, a temporary coexistence between environments could be necessary. Data ownership, cross-system dependencies and transactions across multiple applications need to be managed with care.

3) Prepare the Target Environment Before Moving Production Data

Configure Infrastructure and Database Settings

Provision required infrastructure, install required DB software, configure storage and networking, and set up security controls in advance. Check memory settings, connection limits, database options, character sets, etc. etc. etc.

Prepare Database Objects and Application Dependencies

Wherever possible in the selected migration method, the database objects and application dependencies should be prepared. This involves examining schema compatibility, stored procedures, triggers, scheduled tasks, database permissions and external connections.

Set Up Monitoring and Alerting

Monitoring and alerting should also be set up on the target prior to the start of production traffic. Teams require information on database availability, transaction performance, resource usage, replication status, application errors and more.

Verify Infrastructure Capacity

Infrastructure capacity needs to be verified with representative workloads. Even though it looks healthy in a small test, a target environment could have a problem under production concurrency or under peak transaction volumes.

4) Rehearse the Migration and Measure the Cutover

A migration plan should not be something that is only done once but should be rehearsed repeatedly.

Test With Representative Workloads

Test with a representative test environment, including realistic amounts of data, database objects, application configurations and transaction patterns. If full production-scale testing is impractical, determine the restrictions and include them in the estimate of the duration of the cutovers.

Track the Duration of Each Migration Activity

Keep track of the duration of each of the activities during the rehearsals, including:

• Stopping application writes and background jobs.
• Processing final data synchronisation.
• Validating database consistency.
• Redirecting application connections.
• Restarting process or scheduled processes.
• Creating smoke test and critical business transactions.
• Validating the monitoring and alerting systems are working properly.

These measurements are helpful for team to pinpoint bottlenecks and develop a realistic runbook.

Refine the Cutover Plan

If testing indicates that validation is more time consuming than the final data transfer, for instance, the team should determine if it can start with the validation sooner, if validation can be done incrementally, or if it can be shortened or eliminated without compromising validation.

The final migration procedure needs to assign task owners, dependencies, durations, decision points, communication and rollback triggers. This type of preparation minimizes confusion when decisions have to be made quickly.

5) Synchronize Data and Control Transactions Carefully

The goal of reducing downtime during migrations is a key aspect of data synchronization, which allows the source to stay up and running while the target is getting ready.

Transfer Initial Data Before the Maintenance Window

Initial data transfer can occur prior to the final maintenance window, if applicable for the selected migration technology. This enables the team to transfer significant quantities of data without the application having to be down during the transfer.

Track Changes and Synchronization Lag

Any changes that occur after transfer will need to be recorded and applied properly. The migration team should keep an eye on sync lag and have a clear cutover readiness threshold.

Handle Synchronization Failures Safely

Teams should also know what to do if they fail or interrupter the synchronization. They should be aware that the process can resume safely, how duplicate changes are avoided and how transactions are ordered.

6) Test Application Compatibility Before Production Cutover

Although a successful database is not guaranteed to translate into a successful production application.

Check Connectivity and Database Operations

Applications can rely on database behaviour which varies from one environment to another. Errors that did not occur during data transfer may arise from changes in drivers, connection protocols, authentication, SQL execution plans, transaction handling or configuration settings.

Start with connectivity tests to ensure that applications can log in to the system and connect to it to run simple queries. Then test important database operations, like inserts, updates, deletes, joining, running stored procedures, committing transactions, and rolling them back.

Validate Critical Business Workflows

Business workflow testing is also a key consideration. Order processing system, for instance, ought to be tested from the point that you place your order until you are given confirmation and payment processing takes place. A reporting application should generate output, similar to the business data that is expected.

Compare Performance Against Baselines

The target environment should be compared with the baseline taken during assessment to help improve performance. Analyze variations on response time, locking, transaction throughput, and resource usage on queries that are not as expected.

7) Use Expert Guidance for Complex Migration Projects

Many times, migrations to complex databases are accompanied by applications which need to be migrated, legacy configurations, certain database features, and demanding service availability requirements. An initial assessment may not reveal these risks, whereupon savvy database experts will be able to offer the organization assistance in identifying them.

Work With SAP Sybase Migration Specialists

By partnering with a provider who provides SAP Sybase Consulting services, companies can evaluate their current ASE environment, plan migration activities, measure compatibility, and create a controlled migration plan.

It can be especially helpful when there are custom stored procedures, a high volume of transactions, replication requirements, or applications that can't handle longer outages.

Define Responsibilities Between Internal Teams and Specialists

Clarity of responsibility is a key factor. Business requirements and operational approvals should be owned by the internal team, with technical expertise and execution support provided by the specialists.

Whilst professional help may not remove all migration risks, a systematic and experience-based process can help to increase visibility, decrease avoidable errors and make the migration more predictable.

8) Develop a Detailed Cutover Plan

The point where the production application switches from the original database environment to the target environment is the cutover. This stage should be closely coordinated, even if most migration activities have already been carried out.

There should be a sequence of pre-defined steps in a practical cutover plan.

Before Cutover

Ensure stakeholder consent, maintenance alerts, backup facilities, target readiness, monitoring and having all required personnel present.

Ensure the most recent migration drills are done and that all critical issues have been addressed or accepted.

During Cutover

Stop or slow down application writes as per approved procedure. Complete last synchronization and perform required consistency checks; drain active transactions.

Redirect application connections to the target, following the desired configuration or traffic-switching method, once the target is determined as ready. Re-start dependent services in the proper order and check that applications are able to connect successfully.

Do not make other changes to infrastructure at this time. Configuration changes without a plan can add to uncertainty and difficulty with troubleshooting.

After Cutover

Execute smoke tests as defined and ensure key business processes are operating. Track the amount of errors, transactions, database response time, connection pools, and database resource usage.

The migration lead needs to keep a clear track of what's been done, what's still to do and what are the go/no-go decisions. The team should not improvise under pressure as they would need to follow the documented decision process if a critical validation check fails.

A controlled cutover ensures it can be repeated and all participants know what to do next.

9) Establish a Reliable Rollback and Recovery Strategy

Even with the best test, there are unforeseen problems in even a well-tested migration. A rollback plan describes the organization's approach to dealing with production workloads in a potentially unsafe target environment.

Define Rollback Conditions and Responsibilities

The plan should detail the conditions that would result in rollback, the authority who can decide to roll back, the anticipated recovery time and what actions are to be taken to restore service.

Account for Transactions After Cutover

It is important for the organization to be aware of the implications of any transactions that are made after cutover. Going back to the source may need reverse synchronization, reconciliation, or another well thought-out process, if the target has accepted new writes.

10) Monitor Performance and Stability After Migration

Migration work does not stop when applications start to use the target database. The post-migration period is crucial for discovering potential problems that are only encountered during production workloads.

Monitor Database Health and Performance

Monitor database availability, transaction response times, failed queries, deadlocks, locking contention, CPU utilization, memory usage, storage latency, and connection-pool behavior.

Track Application Performance and Errors

Error rates, user facing response time, failed transactions and background job completion are all metrics to be monitored in applications. If distributed systems are in play, distributed tracing and centralized logging can aid in pinpointing issues across the application and database tiers.

Common Mistakes That Increase Downtime

There are a number of avoidable pitfalls that can result in a manageable migration becoming an extended outage.

Failure to Document Dependencies

Application reliant on scheduled jobs, reporting services, external integrations, database behaviors etc. Do dependency discovery prior to migration.

Not Running Realistic Tests

Not running realistic tests: Using small test databases and workload can miss performance bottlenecks or sync delays. Apply representative test conditions and record any missing conditions.

Waiting to Configure Until the Maintenance Window

Cutover software installation, permissions change or network connectivity problems require precious time. Do these activities beforehand.

Ignoring Data Validation

Data validation is ignored - Data that is successfully transferred does not mean it is accurate or that business tools or relationships are accurate. Identify validations checks that can be measured.

Proceeding Without Decision-Makers

When there is uncertainty about who has the authority, it can lead to delayed decisions. Determine the migration lead, and who has the rights to approve cutover/rollback.

Treating Rollback as a Secondary Consideration

If the target is already accepting new transactions, recovery can be a challenge. Plan and practice recovery before going into production migration.

Preventing these errors ensures optimal operational readiness and contributes to maintaining acceptable downtime.

Conclusion

To minimize downtime during SAP Sybase ASE migration, a coordinated approach including technical preparation, data consistency controls, application testing, and operational discipline is necessary.

The best approach is to take a thorough look at your current situation and understand your business availability requirements. Organizations consider a migration approach that fits their needs, look at target systems beforehand, practice the entire cutover, and create backup and validation mechanisms.

More detail on ASE upgrade planning, compatibility testing, and migration options is available at ralantech.com for teams building their own schedule. Set that target date this week, work backward six months, and book the first compatibility check into the calendar.