Migration assessment TECH PREVIEW

The Voyager Migration Assessment feature streamlines database migration from PostgreSQL and Oracle to YugabyteDB. It analyzes the source database, captures essential metadata, and generates a report with recommended migration strategies and cluster configurations for optimal performance with YugabyteDB.

Overview

When you run an assessment, Voyager gathers key metadata and metrics from the source database, such as table column details, sizes of tables and indexes, and read/write IOPS.

Voyager then generates a report that includes:

• Recommended schema changes: Analyzes compatibility with YugabyteDB, highlighting unsupported features and data types. Also, analyzes the schema for any caveats to ensure smooth migration.
• Recommended cluster sizing: Estimates the resources needed for the target environment based on table sizes, number of tables, and throughput requirements.
• Recommended data distribution: Suggests effective sharding strategies for tables and indexes.
• Performance metrics: Analyzes workload characteristics to recommend optimizations in YugabyteDB.
• Migration time estimate: Provides an estimated time for data import into YugabyteDB based on experimental data.
• Unsupported query constructs: Identifies SQL features and constructs not supported by YugabyteDB, such as advisory locks, system columns, and XML functions, and provides a list of queries containing these constructs.

The following table describes the type of data that is collected during a migration assessment.

Get started with migration assessment

To get started with migration assessment, do the following:

1. Install yb-voyager.

2. Install YugabyteDB to view migration assessment report in the yugabyted UI. Using the yugabyted UI, you can visualize and review the database migration workflow performed by YugabyteDB Voyager.

   1. Start a local YugabyteDB cluster. Refer to the steps described in Use a local cluster.

   2. To see the Voyager migration workflow details in the UI, set the following environment variables before starting the migration:

      export CONTROL_PLANE_TYPE=yugabyted
      export YUGABYTED_DB_CONN_STRING=<ysql-connection-parameters>
      

      Provide the standard PostgreSQL connection parameters, including database, user name, host name, and port. For example, postgresql://yugabyte:yugabyte@127.0.0.1:5433

3. Assess migration - Voyager supports two primary modes for conducting migration assessments, depending on your access to the source database as follows:
   
   

   • With source database connectivity
   • Without source database connectivity

   This mode requires direct connectivity to the source database from the client machine where voyager is installed. You initiate the assessment by executing the assess-migration command of yb-voyager. This command facilitates a live analysis by interacting directly with the source database, to gather metadata required for assessment. A sample command is as follows:

   yb-voyager assess-migration --source-db-type postgresql \
       --source-db-host hostname --source-db-user ybvoyager \
       --source-db-password password --source-db-name dbname \
       --source-db-schema schema1,schema2 --export-dir /path/to/export/dir
   

   PostgreSQL only. In situations where direct access to the source database is restricted, there is an alternative approach. Voyager includes packages with scripts for PostgreSQL at /etc/yb-voyager/gather-assessment-metadata.

   You can perform the following steps with these scripts:

   1. On a machine which has access to the source database, copy the scripts and install dependencies psql and pg_dump version 14 or later. Alternatively, you can install yb-voyager on the machine to automatically get the dependencies.

   2. Run the yb-voyager-pg-gather-assessment-metadata.sh script by providing the source connection string, the schema names, path to a directory where metadata will be saved, and an optional argument of an interval to capture the IOPS metadata of the source (in seconds with a default value of 120). For example,

      /path/to/yb-voyager-pg-gather-assessment-metadata.sh 'postgresql://ybvoyager@host:port/dbname' 'schema1|schema2' '/path/to/assessment_metadata_dir' '60'
      

   3. Copy the metadata directory to the client machine on which voyager is installed, and run the assess-migration command by specifying the path to the metadata directory as follows:

      yb-voyager assess-migration --source-db-type postgresql \
          --assessment-metadata-dir /path/to/assessment_metadata_dir --export-dir /path/to/export/dir
      

   The output of both the methods is a migration assessment report, and its path is printed on the console.

   Important

   For the most accurate migration assessment, the source database must be actively handling its typical workloads at the time the metadata is gathered. This ensures that the recommendations for sharding strategies and cluster sizing are well-aligned with the database's real-world performance and operational needs.

4. View the assessment report.

   Use the YugabyteDB UI to review the assessment report, which includes migration strategies, complexity, and effort estimates.

   After generating the report, navigate to the Migrations tab in the YugabyteDB UI at http://127.0.0.1:15433 to see the available migrations.

   

5. Create a target YugabyteDB cluster as follows:

   1. Create a cluster in Enhanced PostgreSQL Compatibility Mode, based on the sizing recommendations in the assessment report.

      For a universe in YugabyteDB Anywhere, enable compatibility mode by setting flags on the universe.

   2. Create a database with colocation set to TRUE.

      CREATE DATABASE <TARGET_DB_NAME> with COLOCATION=TRUE;
      

6. Proceed with migration with one of the migration workflows:

   • Offline migration
   • Live migration
   • Live migration with fall-forward
   • Live migration with fall-back

Assess a fleet of databases (Oracle only)

Use the Bulk Assessment command (assess-migration-bulk) to assess multiple schemas across one or more database instances simultaneously. It offers:

• Multi-Schema Assessment: Assess multiple schemas in different database instances with a single command, simplifying migration planning.
• Centralized Reporting: All assessment reports are generated and stored in one organized directory, making

Command

To perform a bulk assessment, use the following command syntax:

yb-voyager assess-migration-bulk \
    --fleet-config-file /path/to/fleet_config_file.csv \
    --bulk-assessment-dir /path/to/bulk-assessment-dir \
    [--continue-on-error true|false] \
    [--start-clean true|false]

Fleet configuration file

Bulk assessment is managed using a fleet configuration file, which specifies the schemas to be assessed. The file is in CSV format.

• Header Row: The first row contains headers that define the fields for each schema.
• Schema Rows: Each subsequent row corresponds to a different schema to be assessed.

The following table outlines the fields that can be included in the fleet configuration file.

The following is an example fleet configuration file.

source-db-type,source-db-host,source-db-port,source-db-name,oracle-db-sid,oracle-tns-alias,source-db-user,source-db-password,source-db-schema
oracle,example-host1,1521,ORCL,,,admin,password,schema1
oracle,example-host2,1521,,ORCL_SID,,admin,password,schema2
oracle,,,,,tns_alias,oracle_user,password,schema3

Directory structure

After the bulk assessment is completed, the top-level directory specified using the --bulk-assessment-dir flag includes subdirectories for each assessed schema. Additionally, a top-level report is generated that provides links to the individual assessment reports for each schema.

/bulk-assessment-dir/
├── bulk_assessment_report.html
├── bulk_assessment_report.json
├── DBNAME-SCHEMA1-export-dir/
│    └── assessment/
│          └── reports/
│                 ├── migration_assessment_report.html
│                 └── migration_assessment_report.json
├── SID-SCHEMA2-export-dir/
│    └── assessment/
│          └── reports/
│                 ├── migration_assessment_report.html
│                 └── migration_assessment_report.json
└── logs/
     └── yb-voyager-assess-migration-bulk.log

Learn more

• Assess migration CLI