# Troubleshooting (/docs/orm/v6/prisma-migrate/workflows/troubleshooting) Location: ORM > v6 > Prisma Migrate > Workflows > Troubleshooting This guide describes how to resolve issues with Prisma Migrate in a development environment, which often involves resetting your database. For production-focused troubleshooting, see: * [Production troubleshooting](/orm/v6/prisma-migrate/workflows/patching-and-hotfixing) * [Patching / hotfixing production databases](/orm/v6/prisma-migrate/workflows/patching-and-hotfixing) > [!WARNING] > This guide **does not apply for MongoDB**.
> Instead of `migrate dev`, [`db push`](/orm/v6/prisma-migrate/workflows/prototyping-your-schema) is used for [MongoDB](/orm/v6/overview/databases/mongodb). Handling migration history conflicts [#handling-migration-history-conflicts] A migration history conflict occurs when there are discrepancies between the **migrations folder in the file system** and the **`_prisma_migrations` table in the database**. Causes of migration history conflict in a development environment [#causes-of-migration-history-conflict-in-a-development-environment] * A migration that has already been applied is later modified * A migration that has already been applied is missing from the file system In a development environment, switching between feature branches can result in a history conflict because the `_prisma_migrations` table contains migrations from `branch-1`, and switching to `branch-2` might cause some of those migrations to disappear. > **Note**: You should [never purposefully delete or edit a migration](/orm/v6/prisma-migrate/understanding-prisma-migrate/migration-histories#do-not-edit-or-delete-migrations-that-have-been-applied), as this might result in discrepancies between development and production. Fixing a migration history conflict in a development environment [#fixing-a-migration-history-conflict-in-a-development-environment] If Prisma Migrate detects a migration history conflict when you run `prisma migrate dev`, the CLI will ask to reset the database and reapply the migration history. Schema drift [#schema-drift] Database schema drift occurs when your database schema is out of sync with your migration history - the database schema has 'drifted away' from the source of truth. Causes of schema drift in a development environment [#causes-of-schema-drift-in-a-development-environment] Schema drift can occur if: * The database schema was changed *without* using migrations - for example, by using [`prisma db push`](/orm/v6/reference/prisma-cli-reference#db-push) or manually changing the database schema. > **Note**: The [shadow database](/orm/v6/prisma-migrate/understanding-prisma-migrate/shadow-database) is required to detect schema drift, and can therefore only be done in a development environment. Fixing schema drift in a development environment [#fixing-schema-drift-in-a-development-environment] If you made manual changes to the database that you do not want to keep, or can easily replicate in the Prisma schema: 1. Reset your database: #### npm ```bash npx prisma migrate reset ``` #### pnpm ```bash pnpm dlx prisma migrate reset ``` #### yarn ```bash yarn dlx prisma migrate reset ``` #### bun ```bash bunx --bun prisma migrate reset ``` 2. Replicate the changes in the Prisma schema and generate a new migration: #### npm ```bash npx prisma migrate dev ``` #### pnpm ```bash pnpm dlx prisma migrate dev ``` #### yarn ```bash yarn dlx prisma migrate dev ``` #### bun ```bash bunx --bun prisma migrate dev ``` If you made manual changes to the database that you want to keep, you can: 1. Introspect the database: #### npm ```bash npx prisma db pull ``` #### pnpm ```bash pnpm dlx prisma db pull ``` #### yarn ```bash yarn dlx prisma db pull ``` #### bun ```bash bunx --bun prisma db pull ``` Prisma will update your schema with the changes made directly in the database. 2. Generate a new migration to include the introspected changes in your migration history: #### npm ```bash npx prisma migrate dev --name introspected_change ``` #### pnpm ```bash pnpm dlx prisma migrate dev --name introspected_change ``` #### yarn ```bash yarn dlx prisma migrate dev --name introspected_change ``` #### bun ```bash bunx --bun prisma migrate dev --name introspected_change ``` Prisma Migrate will prompt you to reset, then applies all existing migrations and a new migration based on the introspected changes. Your database and migration history are now in sync, including your manual changes. Failed migrations [#failed-migrations] Causes of failed migrations in a development environment [#causes-of-failed-migrations-in-a-development-environment] A migration might fail if: * You [modify a migration before running it](/orm/v6/prisma-migrate/workflows/customizing-migrations) and introduce a syntax error * You add a mandatory (`NOT NULL`) column to a table that already has data * The migration process stopped unexpectedly * The database shut down in the middle of the migration process Each migration in the `_prisma_migrations` table has a `logs` column that stores the error. Fixing failed migrations in a development environment [#fixing-failed-migrations-in-a-development-environment] The easiest way to handle a failed migration in a developer environment is to address the root cause and reset the database. For example: * If you introduced a SQL syntax error by manually editing the database, update the `migration.sql` file that failed and reset the database: ```bash prisma migrate reset ``` * If you introduced a change in the Prisma schema that cannot be applied to a database with data (for example, a mandatory column in a table with data): 1. Delete the `migration.sql` file. 2. Modify the schema - for example, add a default value to the mandatory field. 3. Migrate: ```bash prisma migrate dev ``` Prisma Migrate will prompt you to reset the database and re-apply all migrations. * If something interrupted the migration process, reset the database: ```bash prisma migrate reset ``` Prisma Migrate and PgBouncer [#prisma-migrate-and-pgbouncer] You might see the following error if you attempt to run Prisma Migrate commands in an environment that uses PgBouncer for connection pooling: ```bash Error: undefined: Database error Error querying the database: db error: ERROR: prepared statement "s0" already exists ``` See [Prisma Migrate and PgBouncer workaround](/orm/v6/prisma-client/setup-and-configuration/databases-connections/pgbouncer) for further information and a workaround. ## Related pages - [`Baselining a database`](https://www.prisma.io/docs/orm/v6/prisma-migrate/workflows/baselining): How to initialize a migration history for an existing database that contains important data. - [`Customizing migrations`](https://www.prisma.io/docs/orm/v6/prisma-migrate/workflows/customizing-migrations): How to edit a migration file before applying it to avoid data loss in production. - [`Data migrations`](https://www.prisma.io/docs/orm/v6/prisma-migrate/workflows/data-migration): How to migrate data using Prisma ORM with the expand and contract pattern. - [`Development and production`](https://www.prisma.io/docs/orm/v6/prisma-migrate/workflows/development-and-production): Development and production - [`Generating down migrations`](https://www.prisma.io/docs/orm/v6/prisma-migrate/workflows/generating-down-migrations): How to generate down migrations