Understanding Altibase Architecture

Hybrid Engine Design

Altibase supports two storage engines: memory tables (volatile, fast) and disk tables (persistent, slower). This hybrid design requires careful schema planning, especially when mixing volatile and persistent workloads in real time.

Core Components

• Server Engine (SQL parser, optimizer, execution engine)
• Memory Manager
• Disk Manager and WAL (Write-Ahead Logging)
• Replication & HA Modules

Common Altibase Issues and Root Causes

1. Query Performance Degradation

Performance drops typically occur due to poor indexing, stale statistics, or memory/disk engine mismatch.

SELECT * FROM trade_data WHERE instrument_id = '1A45';
-- Response time increases under load despite low row count

2. Memory Table Eviction or Data Loss

Because memory tables are volatile, uncommitted transactions or unexpected shutdowns can lead to complete data loss if not carefully managed.

3. Replication Latency

Replication between master and standby may suffer from network delays, large transaction payloads, or excessive redo log generation.

ALTIBASE_RPL_LAG_WARNING: Replication lag exceeds threshold - 5.2 seconds

4. Hybrid Table Mismanagement

Improper table design mixing memory and disk-based tables can cause transaction conflicts, dirty reads, and resource contention.

5. Disk Engine Checkpoint Failures

Failures during checkpointing can lead to inconsistent recovery states, especially when file system IO saturation occurs.

[ALTIBASE][Checkpoint] Failure: Unable to flush pages to disk. I/O Timeout.

Advanced Diagnostic Techniques

1. Using V$ System Views

Leverage views like V$SESSION, V$SQL, and V$TABLE_STATISTICS to analyze query execution and table health.

2. SQL Plan Analysis

Run EXPLAIN PLAN to evaluate index usage and join efficiency. Look for full scans or nested loop joins on large datasets.

3. Monitor Buffer Pools

Use SHOW BUFFERPOOL to monitor memory pressure. High eviction rates may indicate suboptimal memory allocation or large intermediate result sets.

4. Logging and Alerts

Check $ALTIBASE_HOME/trc for detailed logs on replication, checkpointing, and transaction commits. Enable alerts for replication lag and memory overflows.

Step-by-Step Fixes

1. Optimizing Query Performance

• Update table statistics: EXEC UPDATE STATISTICS ON trade_data;
• Create composite indexes based on WHERE clause usage
• Rewrite subqueries into joins or use bind parameters to improve reuse

2. Managing Memory Table Volatility

• Commit frequently or use transaction logging for memory tables
• Back up memory table snapshots if durability is essential
• Use hybrid tables only if persistence trade-offs are understood

3. Resolving Replication Lag

• Increase network bandwidth or reduce redo generation rate
• Batch DML operations instead of issuing single-row updates
• Tune MAX_REDO_BUFFER_SIZE and LOG_WRITE_INTERVAL

4. Fixing Hybrid Table Issues

• Avoid cross-joins between memory and disk tables in critical paths
• Use consistent transaction isolation levels
• Monitor lock contention via V$LOCK

5. Checkpoint Failure Recovery

• Throttle disk I/O using OS-level tools (e.g., ionice)
• Adjust checkpoint frequency via CKPT_INTERVAL
• Pre-allocate disk space and monitor storage health proactively

Best Practices for Long-Term Altibase Management

• Separate OLAP and OLTP workloads by using memory for fast OLTP and disk tables for heavy aggregation
• Automate statistics refreshes during off-peak hours
• Regularly monitor replication with V$REPLICATION
• Test schema changes in staging with full workload replay
• Enable WAL archiving for point-in-time recovery and auditing

Conclusion

Altibase delivers exceptional performance in hybrid database environments, but it requires careful tuning and informed design to maintain stability. From memory table management to replication tuning, the key lies in understanding the hybrid engine internals, leveraging diagnostic tools, and enforcing consistent best practices. Teams that proactively monitor and adapt their Altibase environments can achieve low-latency, high-reliability performance for even the most demanding enterprise applications.

FAQs

1. Can memory tables be made durable in Altibase?

Memory tables are inherently volatile, but you can simulate durability via transaction logs and regular snapshots using export tools.

2. Why is my Altibase replication lagging under moderate load?

Replication lag often stems from redo log congestion or network latency. Optimize DML batching and tune redo buffer sizes to reduce lag.

3. How do I avoid query plan regressions after schema changes?

Always update statistics and review EXPLAIN PLAN outputs after altering schemas or indexes to prevent suboptimal plan selection.

4. What's the best way to monitor memory pressure?

Use SHOW BUFFERPOOL and monitor V$MEMORY_STATISTICS for high eviction or overflow rates. Adjust memory allocation as needed.

5. Can I mix memory and disk tables in the same transaction?

Yes, but it requires caution. Ensure proper isolation and avoid long transactions to prevent lock contention and consistency issues.