# Usage – Data Copy (Variant B / Checkpointing)

## Preconditions

1. **Target database exists** (e.g. UTF-8 collation)
2. **Target schema is deployed** (tables, constraints, indexes, views, procs, triggers, users/roles etc.)
3. You can connect to the SQL Server instance with sufficient permissions.

## Run

Open `scripts/migrate_copy_checkpoint.sql` in SSMS.

At the top configure:

- `@SourceDb` (default: `sysdb_UTF8`)
- `@TargetDb` (default: `sysdb_utf8_jr`)

Optional behavior:

- `@Mode`
  - `RESUME` (default): skip tables already marked `DONE`
  - `RESET`: reset state and rerun all tables

- `@StopOnError`
  - `1` (default): stop on first table error
  - `0`: continue with next tables; check `dbo.MigrationState` afterwards

- `@BatchSize`
  - used for tables with `IDENTITY (int/bigint)` to copy in chunks

Execute the script.

## Monitoring

The script prints progress like:

- `... | TABLE_START | dbo.TableX`
- `... | TABLE_DONE | dbo.TableX | Old=... New=...`
- `... | TABLE_FAILED | dbo.TableX | Error ...`

In target DB you also have:

- `dbo.MigrationState` (table-level status)
- `dbo.MigrationCopyLog` (append-only log)

Useful queries:

```sql
USE sysdb_utf8_jr;
SELECT * FROM dbo.MigrationState ORDER BY Status, TableSchema, TableName;
SELECT TOP 200 * FROM dbo.MigrationCopyLog ORDER BY LogId DESC;
```

## Rerun behavior

Each table is copied as:

1. `DELETE FROM target.table`
2. `INSERT INTO target.table SELECT ... FROM source.table`

So reruns are safe. The checkpoint state enables resuming.