Decision trees

• Slow query: in-depth diagnosis
• Deadlock / lock conflict (ORA-00060, 1213, 40P01)
• Disk / tablespace full
• Connection storm (too many connections)
• Replication lag / stopped
• ORA-01555: Snapshot too old (Oracle)
• Backup & restore decision
• Version upgrade wizard
• Migration wizard (data/schema migration)
• High CPU
• Memory pressure / OOM
• New installation & secure baseline
• Data corruption recovery
• Failover drill / planned role transition
• Security incident / suspicious access
• Audit setup
• Decision: which HA/DR solution?
• Decision: Which isolation level?
• Decision: SQL or NoSQL (which database family)?
• Decision: Sharding or Replication (scaling)?
• Decision: Which backup strategy?
• Decision: Which index type?
• Decision: Which partitioning strategy?
• Decision: How to set up connection pooling?
• Decision: which caching strategy?
• Decision: choose the right data type
• Decision: Server sizing
• Slow writes (INSERT/UPDATE latency)
• High IO wait / disk latency
• Undo / TempDB / temporary space pressure
• Long-running / open transaction
• Query plan regressed (suddenly slow)
• Replica broken / resync needed
• Low cache hit ratio (buffer/cache hit)
• Reference Architecture: 3-tier OLTP application
• Reference Architecture: Data warehouse / analytics
• Reference Architecture: Microservice data layer
• Reference Architecture: Event-driven / CQRS
• Reference Architecture: multi-region / global
• Reference Architecture: high scale / high traffic