Go LATCH waittypes

LATCH waittypes

A latch is a short-term lightweight synchronization object. The following list describes the different types of latches:

• Non-buffer (non-buf) latch:the Non-buffer latches provide synchronization services to in-memory data structures or Provid e re-entrancy protection for concurrency-sensitive code lines. These latches can is used for a variety of things, but they is not used to synchronize access to buffer pages.
• Buffer (BUF) latch:the buffer latches is used to synchronize access to BUF structures and their associated database page S. The typical buffer latching occurs during operations that require serialization on a buffer page, (during a page split or during the allocation of a new page, for example). These latches is not held for the duration of a transaction. These is indicated in the master.dbo.sysprocesses table by the Pagelatch waittypes.
• Io latch:the io latches is a subset of BUF latches that is used when the buffer and associated data page or the index p The middle of an IO operation. Pageiolatch waittypes is used for disk-to-memory transfers and a significant waittime for these waittypes suggests disk I /O subsystem issues.

Latch_x for internal resource synchronization

Pageiolatch_x for synchronizing data pages in disk to memory

Pagelatch_x is used for access synchronization of in-memory data pages.

The following table lists the different latch waittypes that's the notice in the master.dbo.sysprocesses syste m table in SQL Server and SQL Server 2005.

lastwaittype	Waittype	Description
Latch_nl	0x400	Null latch
Latch_kp	0x401	Keep latch
Latch_sh	0x402	Shared latch
Latch_up	0x403	Update latch
Latch_ex	0x404	Exclusive latch
Latch_dt	0x405	Destroy latch
Pagelatch_nl	0x410	Null buffer page latch
Pagelatch_kp	0x411	Keep buffer page latch
Pagelatch_sh	0x412	Shared buffer page latch
Pagelatch_up	0x413	Update buffer page latch
Pagelatch_ex	0x414	Exclusive buffer page latch
Pagelatch_dt	0x415	Destroy buffer page latch
Pageiolatch_nl	0x420	Null buffer page I/O latch
Pageiolatch_kp	0x421	Keep buffer page I/O latch
Pageiolatch_sh	0x422	Shared buffer page I/O latch
Pageiolatch_up	0x423	Update buffer page I/O latch
Pageiolatch_ex	0x424	Exclusive buffer page I/O latch
Pageiolatch_dt	0x425	Destroy buffer page I/O latch

Original: https://support.microsoft.com/en-us/kb/822101

Go LATCH waittypes