This is the full list of warnings generated as part of Schema Compare's deployment analysis. Need a new warning? Let us know on UserVoice.

Learn more about using the Warnings tab in the UI or using the /abortonwarnings command line switch in an automated process.

High - Data loss / safety related warnings

These warnings cover cases where there may be data loss as a result of the requested operation, or the script may fail because it is not clear what to fill a column with.

1. A column could not be matched to columns in the source table. The columns will be dropped, and any data they contain will be lost.
2. Deployment cannot update the A column because it does not allow NULL values. If you run the deployment script, deployment will fail. We recommend you edit the script before running it.
3. Deployment will change partitioning. The table will be rebuilt. We recommend you review the table rebuild script before running it.
4. Deployment cannot change system partitioning of a table. The table cannot be rebuilt, and will not be deployed.
5. Deployment cannot change the REF constraints on a table. If you run the deployment script without making any changes, it may produce unexpected results.
6. Deployment cannot convert one datatype another. If you run the deployment script, data will be lost.
7. Deployment will reduce the width of a column. If there is data in the column, the deployment script will fail. We recommend you edit the script before running it.
8. The current value of a target sequence will be lost because it is not within the MINVALUE and MAXVALUE limits of the source sequence. The current value will be reset to a default value.
9. The current value of a target identity column will be lost because it is not within the MINVALUE and MAXVALUE limits of the source identity column or the range starts before the current value.
10. A datatype is not supported on the target database version. If you run the deployment script, deployment will fail. You are strongly recommended to edit the script before running it.
11. A log group type is not supported on the target database version. If you run the deployment script, deployment will fail. You are strongly recommended to edit the script before running it.
12. A partitioning scheme is not supported on the target database version. If you run the deployment script, deployment will fail. We recommend you edit the script.
13. A virtual column is not supported on the target database version.  If you run the deployment script, deployment will fail. We recommend you edit the script before running it.
14. The table compression option is not supported on the target database version. If you run the deployment script, deployment will fail. We recommend you edit the script before running it.
15. Grants on an object cannot be deployed as the object is not in the target.
16. Grants cannot be applied to a user as it doesn’t exist in the target.
17. A constraint name is already in use in the target database. You must rename the constraint for the script to work.
18. An index name is already in use in the target database. You must rename the index for the script to work.
19. A column will be dropped. Any data in the columns will be lost.
20. A table will be dropped. Any data in the table will be lost.
21. A public synonym will be dropped.
22. A sequence uses 12c or later clause(s) that are not supported on the target database version. The sequence will be deployed without these clauses.
23. A column will be converted to an identity column which does not allow NULL values. If you run the deployment script, deployment will fail if the target table contains NULL in a column. We recommend you review the script before running it.
24. Deployment of an index will fail if its parameters depend on Oracle preferences or parameter content. You need to deploy any dependent preferences or parameter content manually.
25. We are unable to reliably read ILM policies. ILM policies may not synchronise correctly. Connecting as a user that has read access to sys.ilm$ and sys.ilmpolicy$ will fix this issue.

High - Undeployable object warnings

These warnings cover other cases where the source object can't be deployed to the target database, e.g. because of encryption or the options used.

High - Version change warnings

These warnings cover cases when the source database is using a feature that isn't supported in the target database.

Medium - Script may fail

These warnings cover cases where the script may fail to run - e.g. if filegroups are not identical between the databases, or there may be dependencies that can't be identified.

Medium - Potentially unexpected behavior

These warnings cover cases where the script will run, but the behaviour might not be as expected, e.g. because objects cannot be fully compared or deployed.

Medium - Performance warnings

These warnings mostly tell you that we're going to do a table rebuild - creating a new table and transferring all the target data into it, then dropping the old table and renaming - which can be a costly operation in performance terms. We do this when there is no way to use ALTER statements to get your target table into the source state. There are a few other similarly long running operations we also warn you about.

Low - informational warnings

These warnings let you know various things that could potentially make the script fail, or that you might not have expected to happen, but that are unlikely to have a major impact.