Tales From A Lazy Fat DBA

Oracle Database 23c AI introduces a new trailer block format for Data Pump dump files, moving away from the traditional header block approach used in earlier versions like 21c. This new structure is designed specifically to support cloud storage environments, particularly within Oracle Cloud Infrastructure (OCI), and makes it easier to manage and transfer Data Pump files to object stores.

What’s Different with Trailer Blocks?

Trailer blocks are written only once the export process completes, contrasting with header blocks, which required upfront metadata and continuous updates throughout the job. This deferred approach means trailer blocks accumulate necessary metadata during the export process, allowing it to be stored in a more cloud-compatible format at the end. The switch to trailer blocks by default enables seamless storage of dump files in cloud object stores and reduces the limitations associated with local-only file systems.

Note : Trailer block files are compatible only with Oracle Database 23c AI and later. To ensure backward compatibility for previous Oracle versions, you can use the VERSION parameter to revert to the legacy header block format.

How to Use Trailer Blocks with Cloud Object Storage

When running Data Pump in Oracle 23c AI, trailer blocks allow straightforward use with object storage by configuring these essential parameters:

1. Authenticate with Cloud Credentials: Ensure you have a credential object in place to establish the required connection with your object store.
2. Configure DUMPFILE and CREDENTIAL Parameters: List export files using DUMPFILE and specify the credential to direct these files to the cloud.
3. Set Log File Storage: Use the DEFAULT_DIRECTORY parameter to control log file storage. Failing to set up a valid cloud credential for object store URIs will lead to errors in dump file writing.

Steps for Cloud Storage Access

To export files directly to a cloud object store, ensure you have cloud credentials stored in an Oracle Wallet, with the location specified in your sqlnet.ora configuration. You will also need to add a certificate for authentication using orapki:

orapki wallet add -wallet <path_to_wallet> -trusted_cert -cert <certificate_file> -pwd <wallet_password>

This setup allows the Data Pump to use the CREDENTIAL parameter with the export command, establishing secure access to cloud storage.

Header Blocks vs. Trailer Blocks

In Oracle Database versions prior to 23c, Data Pump files used header blocks, where metadata was embedded at the start of each dump file. This format was limited to local storage and required metadata updates during export, which could be resource-intensive.

With Oracle Database 23c AI, trailer blocks are the default. This approach shifts metadata to the end of the file, streamlining the process for cloud storage. By using the VERSION parameter, you can control whether to retain the newer trailer block format or revert to header blocks based on compatibility needs.

Types of Trailer Blocks in Oracle 23c AI

Oracle 23c AI introduces two types of trailer blocks for handling Data Pump files:

• Disk-Based Trailer Blocks: Directly written at the end of each primary table’s data in the dump file, providing a compact storage format.
• Table-Based Trailer Blocks: Stored externally within the export’s primary table, conserving space by omitting individual trailer blocks for each data object. This approach efficiently manages storage while maintaining essential metadata for cloud-based and local export jobs.

Trailer blocks make Data Pump in Oracle Database 23c AI a flexible and cloud-ready solution, enabling efficient data movement across hybrid and cloud infrastructures. This updated approach supports larger cloud-based workflows by improving performance and storage efficiency for Data Pump exports.

Hope It Helped!
Prashant Dixit