DBA Technical Considerations

Every DBA is faced with challenges that could be easily addressed, if only there were enough money. I have rarely heard a DBA complain that a system had too much horsepower or enough disk space. There are certain technical limitations that dictate the type of backup and recovery plan that you implement. For example, one site I worked at had triple the amount of disk space that the database required. That made it easy for us to automate physical image copies of the disks to alternate drives. We then backed up the copies to tape during the day and stored these tapes off site. Most sites don't have this luxury and have to bring their databases down to execute a backup. DBAs have to take all the technical aspects of the operation of their company's business into consideration. Some of the questions a DBA might ask are ?

1. How much disk and data do I have? When will I run out of space?
2. When will I need to upgrade my hardware platform? ?
3. Do I need a standby database? ?
4. What are the likely failure points within my current environment? ?
5. What is my transactional mix?

1. Storage Constraints
   • Disk Space Availability: The amount of storage space affects the type of backup strategy you can use (e.g., full, incremental, or differential backups). Limited storage may require you to use compressed backups or prioritize incremental backups.
   • Growth of Data: Rapidly growing data volumes might require automated space management, archiving strategies, and periodic purging of obsolete data.
2. Backup Time Window
   • System Uptime Requirements: In environments with minimal downtime tolerance, you might rely on online (hot) backups instead of offline (cold) backups.
   • Performance Impact: Large databases can experience performance degradation during backups, especially if sufficient resources are not allocated.
3. Recovery Time Objective (RTO) and Recovery Point Objective (RPO)
   • RTO: The maximum acceptable downtime dictates how quickly the database needs to be restored. High RTO expectations may require fast recovery features, such as Oracle’s Fast Recovery Area (FRA).
   • RPO: The amount of data loss that is tolerable determines how frequently you need to back up the database (e.g., continuous archive log backups or periodic full backups).
4. Infrastructure Limitations
   • Network Bandwidth: For distributed systems, backing up to remote locations or Oracle Cloud can be limited by network speed and reliability.
   • Hardware Performance: Disk speed, memory, and CPU capabilities affect the efficiency of backup and recovery operations.
   • Cloud Storage: Using Oracle Cloud for backups requires proper configurations, and retrieval speed may depend on the service tier.
5. Size and Complexity of the Database
   • Large Database Sizes: Larger databases may require partitioned backups or multisection backups to optimize backup time.
   • Distributed Databases: If using Oracle’s Sharding feature in 23c, you’ll need to consider the backup and recovery processes for individual shards.
6. Use of Advanced Oracle 23c Features
   • Immutable Tablespaces: Oracle 23c supports immutable tablespaces, which cannot be modified after creation. These require special considerations for backup since changes cannot be rolled back.
   • JSON Relational Duality: If leveraging Oracle 23c's JSON Relational Duality feature, backups must account for both relational and JSON data structures to ensure consistent recovery.
   • Temporal Validity: Oracle 23c supports temporal data, requiring advanced point-in-time recovery for consistent historical data.
7. Archivelog Mode
   • Archivelog Mode Enabled: Enables continuous online backups, allowing you to restore up to the last committed transaction. However, managing archive logs requires sufficient disk space.
   • Noarchivelog Mode: Recovery is limited to the last full backup, making this mode unsuitable for systems requiring minimal data loss.
8. Backup and Recovery Tools
   • Oracle Recovery Manager (RMAN): While RMAN is a powerful tool, its advanced features (e.g., block-level recovery, cross-platform backups) may require additional expertise and configuration.
   • Third-Party Tools: Compatibility issues with external tools or scripts could limit your choices for backup strategies.
9. Fast Recovery Area (FRA)
   • FRA Size Limits: The Fast Recovery Area must be adequately sized to store backups, archive logs, and flashback logs. Insufficient FRA space can disrupt backup operations and require frequent cleanups.
10. Data Encryption
    • Encrypted Backups: If you use Transparent Data Encryption (TDE) or encrypted backups, recovery requires secure access to the encryption keys. Loss of keys could result in inaccessible backups.
11. Multi-Tenant Architecture
    • PDBs vs. CDBs: In Oracle 23c, managing backups for a multi-tenant container database (CDB) with multiple pluggable databases (PDBs) requires careful planning. Each PDB might need a separate backup strategy depending on its criticality.
12. Resource Consumption
    • CPU and I/O Load: Backup processes, particularly compressed or encrypted backups, are resource-intensive and may impact database performance during peak usage hours.
13. Flashback Technology Limitations
    • Flashback Logs: Flashback technologies, such as Flashback Database, depend on the availability of flashback logs, which consume additional storage and require proper configuration.
    • Retention Period: Flashback logs are limited by the flashback retention period, which might not align with all recovery requirements.
14. Licensing and Costs
    • Advanced Features: Some advanced backup and recovery features, such as Data Guard or Oracle Cloud Infrastructure Backup, may require additional licensing.
    • Cloud Costs: Using Oracle Cloud for backups involves ongoing costs, which can impact your strategy.
15. Disaster Recovery Requirements
    • Data Guard Configuration: If implementing Oracle Data Guard for disaster recovery, you need to account for synchronous or asynchronous replication performance and network latency.
    • Cross-Region Backups: Backups stored in geographically remote locations can increase recovery time due to transfer delays.

By considering these technical limitations, you can design a backup and recovery plan tailored to your organization's requirements while leveraging Oracle 23c's advanced features effectively.
The next lesson explores the components of an effective disaster recovery plan.

Click the Exercise link below to test your knowledge of the operational and technical considerations of backup and recovery.
Technical Considerations - Exercise