See Also secondary index, stored generated column, virtual generated column. 

Visual Studio 

 For supported versions of Visual Studio, see the following references: 

•Connector/NET: Connector/NET Versions 

•Connector/C++ 8.0: Platform Support and Prerequisites 

See Also Connector/C++, Connector/NET. 

## W 

wait 

 When an operation, such as acquiring a lock , mutex , or latch , cannot be completed immediately, InnoDB pauses and tries again. The mechanism for pausing is elaborate enough that this operation has its own name, the wait . Individual threads are paused using a combination of internal InnoDB  scheduling, operating system wait()  calls, and short-duration spin  loops. 

On systems with heavy load and many transactions, you might use the output from the SHOW INNODB STATUS command or Performance Schema  to determine whether threads are spending too much time waiting, and if so, how you can improve concurrency . See Also concurrency, latch, lock, mutex, Performance Schema, spin. 

warm backup 

 A backup  taken while the database is running, but that restricts some database operations during the backup process. For example, tables might become read-only. For busy applications and websites, you might prefer a hot backup . See Also backup, cold backup, hot backup. 

warm up 

 To run a system under a typical workload  for some time after startup, so that the buffer pool  and other memory regions are filled as they would be under normal conditions. This process happens naturally over time when a MySQL server is restarted or subjected to a new workload. 

Typically, you run a workload for some time to warm up the buffer pool before running performance tests, to ensure consistent results across multiple runs; otherwise, performance might be artificially low during the first run. 

In MySQL 5.6, you can speed up the warmup process by enabling the innodb_buffer_pool_dump_at_shutdown  and innodb_buffer_pool_load_at_startup  configuration options, to bring the contents of the buffer pool back into memory after a restart. These options are enabled by default in MySQL 5.7. See Section 15.8.3.6, “Saving and Restoring the Buffer Pool State” . See Also buffer pool, workload. 

workload 

 The combination and volume of SQL  and other database operations, performed by a database application during typical or peak usage. You can subject the database to a particular workload during performance testing to identify bottlenecks , or during capacity planning. See Also bottleneck, CPU-bound, disk-bound, SQL. 

write combining 

 An optimization technique that reduces write operations when dirty pages  are flushed  from the InnoDB buffer pool . If a row in a page is updated multiple times, or multiple rows on the same page are updated, all of those changes are stored to the data files in a single write operation rather than one write for each change. See Also buffer pool, dirty page, flush. 

