Storage servers and advanced features
IBM® TotalStorage offers many advanced features to further boost performance.
- Extended address volumes (EAV)
- With extended address volumes (EAV), you can store more data that is in VSAM data sets on a single volume than you can store on non-extended address volumes. The maximum amount of data that you can store in a single DB2® table space or index space is the same for extended and non-extended address volumes. The same DB2 data sets might use more space on extended address volumes than on non-extended address volumes because space allocations in the extended area are multiples of 21 cylinders on extended address volumes.
- Parallel Access Volumes (PAV)
- Enables multiple concurrent I/O operations on a device when the I/O requests originate from the same system. Parallel access volumes (PAV) make storing multiple partitions on the same volume with almost no loss of performance possible. In older disk subsystems, if more than one partition is placed on the same volume (intentionally or otherwise), attempts to read the partitions result in contention. The contention shows up as I/O subsystem queue time. Without PAVs, poor placement of a single data set can almost double the elapsed time of a parallel query.
- Multiple allegiance
- Enables multiple active concurrent I/O operations on a single device when the I/O requests originate from different systems. Together, parallel access volumes (PAVs) and multiple allegiance dramatically improve I/O performance for parallel work on the same volume. These features nearly eliminate I/O subsystem queue or PEND time and lower elapsed time for transactions and queries.
- FlashCopy®
- Provides for fast copying of full volumes. After an initialization period is complete, the logical copy is considered complete but the physical movement of the data is deferred.
- Peer-to-Peer Remote Copy (PPRC)
- Provide a faster method for recovering DB2 subsystems at a remote site in the event of a disaster at a local site.
Other storage servers might offer similar functions.