Partitioning and LOB Data in Oracle

Partitioning and LOB Data in Oracle

Partitioned Tables

Most tables can be partitioned.

Any table can be partitioned up to a million separate partitions except those tables containing columns with LONG or LONG RAW data types. You can, however, use tables containing columns with CLOB or BLOB data types.

Note: To reduce disk and memory usage (specifically, the buffer cache), you can store tables and partitions of a partitioned table in a compressed format inside the database. This often improves scaleup for read-only operations. Table compression can also speed up query execution. There is, however, a slight cost in CPU overhead.

When to Partition a Table

There are certain situations when you would want to partition a table.

Here are some suggestions for situations when you should consider partitioning a table:

• Tables that are greater than 2 GB.

These tables should always be considered as candidates for partitioning.

• Tables that contain historical data, in which new data is added into the newest partition.

A typical example is a historical table where only the current month's data is updatable and the other 11 months are read only.

• Tables whose contents must be distributed across different types of storage devices.

Partitioning and LOB Data in Oracle

Unstructured data, such as images, videos, and documents, is often stored in LOB (Large Object) columns within an Oracle database. Oracle allows not only the partitioning of relational data but also the partitioning and separate management of LOB data.

When a table is partitioned, all of its columns typically reside in the tablespace for that partition. However, LOB columns have a unique advantage: they can be stored in separate tablespaces that are independent from the main partitioned data.

This separation becomes especially valuable when working with tables that contain very large LOBs. By storing LOBs separately from the main row data, administrators can optimize both performance and cost efficiency.

For instance, if the primary row data is updated frequently but the LOB data remains relatively static, this approach ensures that heavy LOB storage does not impact routine updates.

Consider an example of an employee table. Each record may include an employee’s photo stored as a BLOB, alongside personnel details such as name, address, department, and manager. The personnel details are subject to frequent updates, while the photo is unlikely to change. By storing the LOB column (the photo) in a separate tablespace, updates to the employee record remain lightweight and efficient.

Another advantage is tiered storage management. LOB data can be placed on less expensive, slower storage devices, while the main employee records can reside on high-performance storage. This ensures that critical transactional data benefits from speed, while large, less frequently accessed objects do not consume costly resources.

In summary, Oracle’s ability to partition and separately store LOB data provides organizations with flexibility, performance optimization, and cost control. This strategy is particularly effective in systems where structured data changes regularly, but unstructured LOB data remains relatively stable.

Benefits of Partitioning

Partitioning can provide tremendous benefit to a wide variety of applications by improving performance, manageability, and availability.

It is not unusual for partitioning to greatly improve the performance of certain queries or maintenance operations. Moreover, partitioning can greatly simplify common administration tasks.

Partitioning also enables database designers and administrators to solve some difficult problems posed by cutting-edge applications. Partitioning is a key tool for building multi-terabyte systems or systems with extremely high availability requirements.

Partitioning and LOB Data in Oracle

Unstructured data, such as images, videos, and documents, is often stored in LOB (Large Object) columns within an Oracle database. Oracle not only supports partitioning for relational (structured) data but also provides mechanisms to partition and manage LOB data more effectively. This capability helps organizations improve performance, manageability, and storage costs when dealing with large volumes of binary or multimedia content.

Storing LOBs in Separate Tablespaces

When a table is partitioned in Oracle, all of its columns typically reside in the same tablespace for that partition. However, LOB columns have the unique ability to be stored in separate tablespaces, independent of the main row data.

This separation becomes highly beneficial in cases where tables contain large LOBs. For example:

• Main row data (employee details such as name, address, and department) may be updated frequently.
• LOB data (such as an employee’s photo) is far less likely to change.

By storing the photo (BLOB) in a separate tablespace, updates to the main employee record remain lightweight and efficient, avoiding unnecessary I/O overhead from the larger LOB data.

Additionally, this strategy enables tiered storage optimization:

• Fast, expensive storage can be allocated to the transactional row data that changes frequently.
• Cheaper, slower storage can be used for LOB data that is accessed less often.

This separation reduces costs while maintaining high performance for critical workloads.

Oracle SecureFiles and Partitioned LOBs

Modern Oracle implementations recommend the use of SecureFiles over BasicFiles for managing LOBs. SecureFiles not only provide performance improvements but also include advanced features such as:

• Compression – Reduces storage requirements.
• Deduplication – Prevents redundant LOB storage.
• Encryption – Secures sensitive unstructured data.
• Partitioned LOBs – Distributes LOBs across multiple partitions for scalability.

Partitioned SecureFiles enable administrators to organize large object data more intelligently, aligning storage with business and performance needs.

 

LOB Partitioning Strategies

Oracle supports multiple partitioning methods for tables containing LOB columns, which can also extend to the LOB data itself. Choosing the right partitioning strategy depends on the data distribution and query patterns:

1. Range Partitioning
• LOBs are distributed based on a range of values (e.g., partitioning employee photos by hire date).
• Useful for time-based queries and archiving older data.
2. List Partitioning
• LOBs are grouped into partitions based on discrete values (e.g., file type: images, PDFs, or audio).
• Provides logical grouping for specific categories of data.
3. Hash Partitioning
• LOBs are evenly distributed across partitions using a hashing algorithm.
• Prevents data skew and balances I/O workload across partitions.
4. Composite Partitioning
• Combines methods (e.g., range-hash) for greater control.
• Example: Partition employee documents by year (range) and distribute them evenly across storage (hash).

Benefits of Partitioning LOB Data

• Performance Optimization – Queries scan only relevant partitions instead of the entire dataset.
• Parallelism – Partitioned LOBs enable Oracle to perform operations across multiple partitions in parallel.
• Improved Manageability – Partitions can be archived, backed up, or purged independently.
• Cost Efficiency – Large, less frequently accessed LOB partitions can be placed on cheaper storage tiers.
• Reduced Contention – Partition-level operations minimize locking conflicts during updates.

Use Case Example

Consider an HR application:

• Employee details (address, job title, department) change frequently.
• Employee documents (contracts, scanned IDs, certificates) are stored as BLOBs but rarely updated.

By storing the structured data in a partitioned table and separating the LOB columns into their own partitioned SecureFiles storage, the application achieves:

• Faster updates to personnel details.
• Efficient storage for documents.
• The ability to move older, rarely accessed documents into archival storage tiers without disrupting the main HR system.

LOB Storage in Separate Tablespaces

• When you create or alter a partitioned table, you can specify the LOB storage clause (STORE AS) separately.
• You can assign each LOB (or partitioned LOB) to its own tablespace, which can differ from the tablespace of the main row data.

2. Compression for LOBs

• Oracle BasicFiles LOBs support only dedicated or shared storage, but not compression.
• Oracle SecureFiles LOBs (introduced in 11g) support:
• COMPRESS – Reduces storage footprint.
• DEDUPLICATE – Avoids redundant copies.
• ENCRYPT – Provides data security.
• Compression works at the LOB level, not at the row-level data.

3. Example: Partitioned Table with LOBs in Compressed Tablespace

CREATE TABLE employee_docs

(

   emp_id        NUMBER,

   emp_name      VARCHAR2(100),

   hire_date     DATE,

   resume        BLOB

)

PARTITION BY RANGE (hire_date)

(

   PARTITION p1 VALUES LESS THAN (DATE '2020-01-01')

      TABLESPACE tbs_fast,

   PARTITION p2 VALUES LESS THAN (DATE '2023-01-01')

      TABLESPACE tbs_fast,

   PARTITION p3 VALUES LESS THAN (MAXVALUE)

      TABLESPACE tbs_fast

)

LOB (resume) STORE AS SECUREFILE resume_seg

(

   TABLESPACE tbs_lob_compressed

   ENABLE STORAGE IN ROW

   COMPRESS HIGH

   CHUNK 8192

   RETENTION

);

4. Benefits

• Performance isolation: OLTP operations on main table data are not slowed by large LOB I/O.
• Storage optimization: Compressed LOBs in a dedicated tablespace reduce storage usage.
• Flexibility: You can move, archive, or back up LOB tablespaces separately.

Conclusion

Unstructured data, such as images and documents, which is stored in a LOB column in a database can also be partitioned.

When a table is partitioned, all of the columns reside in the tablespace for that partition, except LOB columns, which can be stored in their own tablespace.

Oracle’s support for partitioning LOB data represents a powerful solution for enterprises managing large volumes of unstructured data. By separating LOBs into dedicated partitions and leveraging SecureFiles features such as compression, deduplication, and encryption, organizations can achieve better scalability, performance, and cost optimization.

As multimedia and unstructured data continue to grow in enterprise systems, LOB partitioning combined with SecureFiles provides the flexibility to balance fast transactional performance with efficient long-term data storage, ensuring both technical efficiency and business value.