IBM BPM, V8.0.1, All platforms > Tuning > Advanced tuning
Database: general tuning
A set of considerations apply for tuning databases.
- Provide adequate statistics for optimization
Databases often have a wide variety of available choices when determining the best approach for accessing data. Statistics, which describe the "shape" of the data, can be used to guide the selection of a low-cost data access strategy.- Place database log files on a fast disk subsystem
Databases are designed for high availability, transactional processing and recoverability. For recoverability and transaction management, changes to table data are written to the log before being written to DASD.- Place logs on separate devices from table space containers
A basic strategy for all database storage configurations is to place the database logs on separate physical disk devices from the table space containers.- Provide sufficient physical memory
Accessing data in memory is much faster than reading it from disk. With 64-bit hardware being readily available and memory prices continuing to fall, for many performance-critical workloads it makes sense to provision enough memory to avoid most disk reads in steady state.- Avoid double buffering
Because the database attempts to keep frequently accessed data in memory, in most cases there is no benefit to using file system caching. In fact, performance typically improves by using direct input/output (I/O), when files read by the database bypass the file system cache and only one copy of the data is held in memory. This allows more memory to be given to the database and avoids memory overruns in the file system as it manages its cache.- Refine table indexes as required
Business Process Management products typically provide a reasonable set of indexes for the database tables they use. In general, creating indexes involves a tradeoff between the cost of queries and the cost of statements that insert, update, or delete data.