Data Storage

CygNet Software uses Microsoft’s Extensible Storage Engine (ESE) data storage technology for its Value History Service database technology. ESE is used for all CygNet’s database services and offers the following advantages to the VHS:

• Robustness — ESE is extremely robust with ACID compliance (Atomicity, Consistency, Isolation, and Durability), improved performance in database startup times, improved data retrieval speed, and a powerful crash recovery mechanism.
• Capacity — The ESE-based datastore supports very large database sizes. The maximum size of a VHS datastore is 5000 GB (5 TB).
• Extensibility — An ESE-based datastore will support future data structure extensions.
• Reliability — ESE has been the underlying data storage technology of several core Windows components including Microsoft Exchange Server, Active Directory, and many other Microsoft Windows components since the release of Windows 2000.

Older versions of CygNet used a legacy data storage technology for its VHS. The ESE-based VHS requires more disk space than the VHS legacy datastore due to its large number of transaction log files. Because of this, ensure that you have enough available disk space for your ESE-based VHS; we recommend at least twice the disk space of the old datastore.

VHS File Synchronization

The VHS data files consist of the main data storage file (history.edb) and the transaction log files (\txlogs directory and files), which is by default in the service’s data directory. The directory location for the transaction log files is set with the service configuration keyword VHS_TRANSACTION_LOG_DIR. The default value for this keyword is \txlogs and is set in the service’s configuration file (Vhs.cfg). However, if you prefer to store the transaction log files in another location, you may do so.

These files work together to store all historical data. See How ESE Works and ESE File Types for more information about the database engine operation.