Knowledge: Important SQL Server wait types and details.

Top 10 potential SQL Server waits:

Wait_Type	Description
CXPACKET	This wait type always occurs when parallelism happens, as the control thread in a parallel operation waits until all threads have completed.
ASYNC_NETWORK_IO	Occurs on network writes when the task is blocked behind the network. Verify that the client is processing data from the server.
BACKUPIO	Occurs when a backup task is waiting for data, or is waiting for a buffer in which to store data. This type is not typical, except when a task is waiting for a tape mount.
IO_COMPLETION	Occurs while waiting for I/O operations to complete. This wait type generally represents non-data page I/Os. Data page I/O completion waits appear as PAGEIOLATCH_* waits.
PAGEIOLATCH_SH	Occurs when a task is waiting on a latch for a buffer that is in an I/O request. The latch request is in Shared mode. Long waits may indicate problems with the disk subsystem.
PAGELATCH_EX	The classic cause of this wait type are from lots of concurrent threads inserting small rows into a clustered index with an identity value, leading to contention on the index leaf-level pages.
PAGEIOLATCH_EX	Occurs when a task is waiting on a latch for a buffer that is in an I/O request. The latch request is in Exclusive mode. Long waits may indicate problems with the disk subsystem.
WRITELOG	Occurs while waiting for a log flush to complete. Common operations that cause log flushes are checkpoints and transaction commits.
LCK_M_IX	This wait type occurs when a thread is waiting for a table or page IX lock so that a row insert or update can occur. It could be from lock escalation to a table X or S lock causing all other threads to wait to be able to insert/update.
SOS_SCHEDULER_YIELD	This wait type is most often associated with high signal wait rather than waits on a specific resource. If you observe this wait type persistently, investigate for other evidence that may confirm the server is under CPU pressure.