诊断 tempdb 争用和空间使用

命令

-- 1) Current tempdb page latch waits (2:1:1 PFS, 2:1:2 GAM, 2:1:3 SGAM):
SELECT wt.session_id, wt.wait_type, wt.wait_duration_ms, wt.resource_description
FROM   sys.dm_os_waiting_tasks wt
WHERE  wt.wait_type LIKE N'PAGELATCH[_]%'
  AND  wt.resource_description LIKE N'2:%';

-- 2) Sessions using the most tempdb (MB):
SELECT TOP (20) su.session_id, s.login_name, s.program_name,
       (su.user_objects_alloc_page_count - su.user_objects_dealloc_page_count) * 8 / 1024         AS user_obj_mb,
       (su.internal_objects_alloc_page_count - su.internal_objects_dealloc_page_count) * 8 / 1024 AS internal_obj_mb
FROM   sys.dm_db_session_space_usage su
  JOIN sys.dm_exec_sessions s ON s.session_id = su.session_id
WHERE  s.is_user_process = 1
ORDER BY su.user_objects_alloc_page_count + su.internal_objects_alloc_page_count
       - su.user_objects_dealloc_page_count - su.internal_objects_dealloc_page_count DESC;

-- 3) Overall breakdown and version store:
SELECT SUM(unallocated_extent_page_count) * 8 / 1024       AS free_mb,
       SUM(user_object_reserved_page_count) * 8 / 1024     AS user_obj_mb,
       SUM(internal_object_reserved_page_count) * 8 / 1024 AS internal_obj_mb,
       SUM(version_store_reserved_page_count) * 8 / 1024   AS version_store_mb
FROM   tempdb.sys.dm_db_file_space_usage;

SELECT DB_NAME(database_id) AS db, reserved_page_count * 8 / 1024 AS version_store_mb
FROM   sys.dm_tran_version_store_space_usage
ORDER BY reserved_page_count DESC;

-- 4) File count / equal sizing and memory-optimized metadata:
SELECT name, type_desc, size * 8 / 1024 AS size_mb, growth * 8 / 1024 AS growth_mb, is_percent_growth
FROM   tempdb.sys.database_files;
SELECT SERVERPROPERTY('IsTempdbMetadataMemoryOptimized') AS tempdb_metadata_memopt;

作用

显示 tempdb 分配页（PFS/GAM/SGAM）和系统表上的 PAGELATCH 等待、使用 tempdb 最多的会话（临时表与排序/哈希溢出）、哪个数据库在撑大版本存储，以及文件配置。

适用场景

大量临时表负载下 PAGELATCH_UP/EX 等待上升、tempdb 写满（1105/9002）或版本存储增长时。

注意

页 2:1:1、2:1:2、2:1:3 以及位于 8088 倍数处的 PFS 页表示分配争用：解决办法是使用多个大小相同、增长相同的数据文件（每核一个，最多 8 个，之后每次加 4 个）。对于系统表页上的争用，2019+ 提供内存优化的 tempdb 元数据（需要重启）。若版本存储增长，找出最老的打开快照事务；收缩 tempdb 不是解决办法。只读查询；安全。