原文: SQL Server系统视图sys.master_files不能正确显示数据库脱机状态 最近发现在SQL Server数据库（目前测试过SQL Server 2008, 2012，2014，2016各个版本）中，即使数据库处于脱机（OFFLINE）状态，但是sys.master_files中依然显示是联机状态。本文测试环境为Microsoft SQL Server 2014 (SP2) (KB3171021) - 12.0.5000.0 (X64) 。具体测试过程如下所示：
USE master; GO ALTER DATABASE TEST SET OFFLINE WITH ROLLBACK IMMEDIATE; GO SELECT name , physical_name , state , state_desc FROM sys.master_files WHERE database_id = DB_ID('test'); SELECT name , state , state_desc FROM sys.databases WHERE name = 'test'; 
如上所示，sys.databases系统视图正确的显示数据库处于脱机状态(OFFLINE)，但是系统视图sys.master_files显示的依然是联机（ONLINE），我们可以获取系统视图sys.master_files的定义，如下所示（至于如何获取视图定义，如果你不清楚，可以参考我的博客
SQL Server查看视图定义总结），
SET QUOTED_IDENTIFIER ON SET ANSI_NULLS ON GO CREATE VIEW sys.master_files AS SELECT database_id = f.dbid, file_id = f.fileid, file_guid = f.fileguid, type = f.filetype, type_desc = ft.name, data_space_id = f.grpid, name = f.lname, physical_name = f.pname, state = convert(tinyint, case f.filestate -- Map enum EMDFileState to AvailablityStates when 0 then 0 when 10 then 0 -- ONLINE when 4 then 7 -- DEFUNCT when 5 then 3 when 9 then 3 -- RECOVERY_PENDING when 7 then 1 when 8 then 1 when 11 then 1 -- RESTORING when 12 then 4 -- SUSPECT else 6 end), -- OFFLINE state_desc = st.name, f.size, max_size = f.maxsize, f.growth, is_media_read_only = sysconv(bit, f.status & 8), -- FIL_READONLY_MEDIA is_read_only = sysconv(bit, f.status & 16), -- FIL_READONLY is_sparse = sysconv(bit, f.status & 256), -- FIL_SPARSE_FILE is_percent_growth = sysconv(bit, f.status & 32), -- FIL_PERCENT_GROWTH is_name_reserved = sysconv(bit, case f.filestate when 3 then 1 else 0 end), -- x_efs_DroppedReusePending create_lsn = GetNumericLsn(f.createlsn), drop_lsn = GetNumericLsn(f.droplsn), read_only_lsn = GetNumericLsn(f.readonlylsn), read_write_lsn = GetNumericLsn(f.readwritelsn), differential_base_lsn = GetNumericLsn(f.diffbaselsn), differential_base_guid = f.diffbaseguid, differential_base_time = nullif(f.diffbasetime, 0), redo_start_lsn = GetNumericLsn(f.redostartlsn), redo_start_fork_guid = f.redostartforkguid, redo_target_lsn = GetNumericLsn(f.redotargetlsn), redo_target_fork_guid = f.forkguid, backup_lsn = GetNumericLsn(f.backuplsn), credential_id = cr.credential_id FROM sys.sysbrickfiles f LEFT JOIN sys.syspalvalues st ON st.class = 'DBFS' AND st.value = f.filestate LEFT JOIN sys.syspalvalues ft ON ft.class = 'DBFT' AND ft.value = f.filetype LEFT JOIN sys.credentials cr ON f.pname LIKE cr.name + N'%' COLLATE database_default WHERE f.dbid < 0x7fff -- consistent with sys.databases AND f.pruid = 0 AND f.filestate NOT IN (1, 2) -- x_efs_Dummy, x_efs_Dropped AND has_access('MF', 1) = 1 GO 可以看出sys.master_files的state值来自于系统基表sys.sysbrickfiles的filestate字段，我们从DAC模式去查看，发现TEST数据库（dbid=21)的filestat为0，这个值应该为6才对，另外，还有一个让人意外的是，这个系统表里面关于TEST数据库有两个事务日志文件记录，实际上只有一个（其实这个是前阵子写这篇博客“MS SQL 事务日志管理小结”时，测试添加、删除数据事务日志文件遗留下来的记录，不清楚是Bug还是什么问题导致在系统基表还存在这样的一条记录）
那么我们接下来看看sys.sysbrickfiles的具体定义，如下所示：
SET QUOTED_IDENTIFIER ON SET ANSI_NULLS ON GO CREATE VIEW sys.databases AS SELECT d.name, d.id AS database_id, r.indepid AS source_database_id, d.sid AS owner_sid, d.crdate AS create_date, d.cmptlevel AS compatibility_level, -- coll.value = null means that a collation wasn't specified for the DB and the server default is used instead convert(sysname, case when serverproperty('EngineEdition') = 5 AND d.id = 1 then serverproperty('collation') else CollationPropertyFromID(convert(int, isnull(coll.value, p.cid)), 'name') end) AS collation_name, p.user_access, ua.name AS user_access_desc, sysconv(bit, d.status & 0x400) AS is_read_only, -- DBR_RDONLY sysconv(bit, d.status & 1) AS is_auto_close_on, -- DBR_CLOSE_ON_EXIT sysconv(bit, d.status & 0x400000) AS is_auto_shrink_on, -- DBR_AUTOSHRINK case when (serverproperty('EngineEdition') = 5) AND (sysconv(bit, d.status & 0x00000020) = 1) then cast (1 as tinyint) -- RESTORING when (serverproperty('EngineEdition') = 5) AND (sysconv(bit, d.status & 0x00000080) = 1) then cast (7 as tinyint) -- COPYING when (serverproperty('EngineEdition') = 5) AND (sysconv(bit, d.status & 0x00000100) = 1) then cast (4 as tinyint) -- SUSPECT else p.state end AS state, -- 7 is COPYING and 4 is SUSPECT state for database copy (UNDO: Need to have a clean way to set states in dbtable for a user db) case when (serverproperty('EngineEdition') = 5) AND (sysconv(bit, d.status & 0x00000020) = 1) then 'RESTORING' when (serverproperty('EngineEdition') = 5) AND (sysconv(bit, d.status & 0x00000080) = 1) then 'COPYING' when (serverproperty('EngineEdition') = 5) AND (sysconv(bit, d.status & 0x00000100) = 1) then 'SUSPECT' else st.name end AS state_desc, sysconv(bit, d.status & 0x200000) AS is_in_standby, -- DBR_STANDBY case when serverproperty('EngineEdition') = 5 then convert(bit, 0) else p.is_cleanly_shutdown end AS is_cleanly_shutdown, sysconv(bit, d.status & 0x80000000) AS is_supplemental_logging_enabled, -- DBR_SUPPLEMENT_LOG p.snapshot_isolation_state, si.name AS snapshot_isolation_state_desc, sysconv(bit, d.status & 0x800000) AS is_read_committed_snapshot_on, -- DBR_READCOMMITTED_SNAPSHOT p.recovery_model, ro.name AS recovery_model_desc, p.page_verify_option, pv.name AS page_verify_option_desc, sysconv(bit, d.status2 & 0x1000000) AS is_auto_create_stats_on, -- DBR_AUTOCRTSTATS sysconv(bit, d.status2 & 0x00400000) AS is_auto_create_stats_incremental_on, -- DBR_AUTOCRTSTATSINC sysconv(bit, d.status2 & 0x40000000) AS is_auto_update_stats_on, -- DBR_AUTOUPDSTATS sysconv(bit, d.status2 & 0x80000000) AS is_auto_update_stats_async_on, -- DBR_AUTOUPDSTATSASYNC sysconv(bit, d.status2 & 0x4000) AS is_ansi_null_default_on, -- DBR_ANSINULLDFLT sysconv(bit, d.status2 & 0x4000000) AS is_ansi_nulls_on, -- DBR_ANSINULLS sysconv(bit, d.status2 & 0x2000) AS is_ansi_padding_on, -- DBR_ANSIPADDING sysconv(bit, d.status2 & 0x10000000) AS is_ansi_warnings_on, -- DBR_ANSIWARNINGS sysconv(bit, d.status2 & 0x1000) AS is_arithabort_on, -- DBR_ARITHABORT sysconv(bit, d.status2 & 0x10000) AS is_concat_null_yields_null_on, -- DBR_CATNULL sysconv(bit, d.status2 & 0x800) AS is_numeric_roundabort_on, -- DBR_NUMEABORT sysconv(bit, d.status2 & 0x800000) AS is_quoted_identifier_on, -- DBR_QUOTEDIDENT sysconv(bit, d.status2 & 0x20000) AS is_recursive_triggers_on, -- DBR_RECURTRIG sysconv(bit, d.status2 & 0x2000000) AS is_cursor_close_on_commit_on, -- DBR_CURSCLOSEONCOM sysconv(bit, d.status2 & 0x100000) AS is_local_cursor_default, -- DBR_DEFLOCALCURS sysconv(bit, d.status2 & 0x20000000) AS is_fulltext_enabled, -- DBR_FTENABLED sysconv(bit, d.status2 & 0x200) AS is_trustworthy_on, -- DBR_TRUSTWORTHY sysconv(bit, d.status2 & 0x400) AS is_db_chaining_on, -- DBR_DBCHAINING sysconv(bit, d.status2 & 0x08000000) AS is_parameterization_forced, -- DBR_UNIVERSALAUTOPARAM sysconv(bit, d.status2 & 64) AS is_master_key_encrypted_by_server, -- DBR_MASTKEY sysconv(bit, d.status2 & 0x00000010) AS is_query_store_on, -- DBR_QDSENABLED sysconv(bit, d.category & 1) AS is_published, sysconv(bit, d.category & 2) AS is_subscribed, sysconv(bit, d.category & 4) AS is_merge_published, sysconv(bit, d.category & 16) AS is_distributor, sysconv(bit, d.category & 32) AS is_sync_with_backup, d.svcbrkrguid AS service_broker_guid, sysconv(bit, case when d.scope = 0 then 1 else 0 end) AS is_broker_enabled, p.log_reuse_wait, lr.name AS log_reuse_wait_desc, sysconv(bit, d.status2 & 4) AS is_date_correlation_on, -- DBR_DATECORRELATIONOPT sysconv(bit, d.category & 64) AS is_cdc_enabled, sysconv(bit, d.status2 & 0x100) AS is_encrypted, -- DBR_ENCRYPTION convert(bit, d.status2 & 0x8) AS is_honor_broker_priority_on, -- DBR_HONORBRKPRI sgr.guid AS replica_id, sgr2.guid AS group_database_id, ssr.indepid AS resource_pool_id, default_language_lcid = case when ((d.status2 & 0x80000)=0x80000 AND p.containment = 1) then convert(smallint, p.default_language) else null end, default_language_name = case when ((d.status2 & 0x80000)=0x80000 AND p.containment = 1) then convert(sysname, sld.name) else null end, default_fulltext_language_lcid = case when ((d.status2 & 0x80000)=0x80000 AND p.containment = 1) then convert(int, p.default_fulltext_language) else null end, default_fulltext_language_name = case when ((d.status2 & 0x80000)=0x80000 AND p.containment = 1) then convert(sysname, slft.name) else null end, is_nested_triggers_on = case when ((d.status2 & 0x80000)=0x80000 AND p.containment = 1) then convert(bit, p.allow_nested_triggers) else null end, is_transform_noise_words_on = case when ((d.status2 & 0x80000)=0x80000 AND p.containment = 1) then convert(bit, p.transform_noise_words) else null end, two_digit_year_cutoff = case when ((d.status2 & 0x80000)=0x80000 AND p.containment = 1) then convert(smallint, p.two_digit_year_cutoff) else null end, containment = sysconv(tinyint, (d.status2 & 0x80000)/0x80000), -- DBR_IS_CDB containment_desc = convert(nvarchar(60), cdb.name), p.recovery_seconds AS target_recovery_time_in_seconds, p.delayed_durability, case when (p.delayed_durability = 0) then CAST('DISABLED' AS nvarchar(60)) -- LCOPT_DISABLED when (p.delayed_durability = 1) then CAST('ALLOWED' AS nvarchar(60)) -- LCOPT_ALLOWED when (p.delayed_durability = 2) then CAST('FORCED' AS nvarchar(60)) -- LCOPT_FORCED else NULL end AS delayed_durability_desc, convert(bit, d.status2 & 0x80) AS is_memory_optimized_elevate_to_snapshot_on -- DBR_HKELEVATETOSNAPSHOT FROM sys.sysdbreg d OUTER APPLY OpenRowset(TABLE DBPROP, (case when serverproperty('EngineEdition') = 5 then DB_ID() else d.id end)) p LEFT JOIN sys.syssingleobjrefs r ON r.depid = d.id AND r.class = 96 AND r.depsubid = 0 -- SRC_VIEWPOINTDB LEFT JOIN sys.syspalvalues st ON st.class = 'DBST' AND st.value = p.state LEFT JOIN sys.syspalvalues ua ON ua.class = 'DBUA' AND ua.value = p.user_access LEFT JOIN sys.syspalvalues si ON si.class = 'DBSI' AND si.value = p.snapshot_isolation_state LEFT JOIN sys.syspalvalues ro ON ro.class = 'DBRO' AND ro.value = p.recovery_model LEFT JOIN sys.syspalvalues pv ON pv.class = 'DBPV' AND pv.value = p.page_verify_option LEFT JOIN sys.syspalvalues lr ON lr.class = 'LRWT' AND lr.value = p.log_reuse_wait LEFT JOIN sys.syssingleobjrefs agdb ON agdb.depid = d.id AND agdb.class = 104 AND agdb.depsubid = 0 -- SRC_AVAILABILITYGROUP LEFT JOIN master.sys.syssingleobjrefs ssr ON ssr.class = 108 AND ssr.depid = d.id -- SRC_RG_DB_TO_POOL LEFT JOIN master.sys.sysclsobjs ag ON ag.id = agdb.indepid AND ag.class = 67 -- SOC_AVAILABILITY_GROUP LEFT JOIN master.sys.sysguidrefs sgr ON sgr.class = 8 AND sgr.id = ag.id AND sgr.subid = 1 -- GRC_AGGUID / AGGUID_REPLICA_ID LEFT JOIN master.sys.sysguidrefs sgr2 ON sgr2.class = 9 AND sgr2.id = ag.id AND sgr2.subid = d.id -- GRC_AGDBGUID LEFT JOIN sys.syspalvalues cdb ON cdb.class = 'DCDB' AND cdb.value = CASE WHEN (d.status2 & 0x80000)=0x80000 THEN 1 ELSE 0 END LEFT JOIN sys.syslanguages sld ON sld.lcid = p.default_language LEFT JOIN sys.fulltext_languages slft ON slft.lcid = p.default_fulltext_language LEFT JOIN sys.sysobjvalues coll ON coll.valclass = 102 AND coll.subobjid = 0 AND coll.objid = d.id -- SVC_DATACOLLATION WHERE d.id < 0x7fff AND has_access('DB', (case when serverproperty('EngineEdition') = 5 then DB_ID() else d.id end)) = 1 GO | EngineEdition | 服务器上安装的 数据库引擎 实例的 SQL Server版本。 1 = Personal 或 Desktop Engine（不适用于 SQL Server 2005?和更高版本。） 2 = Standard（对 Standard、Web 和 Business Intelligence 返回该值。） 3 = Enterprise（对 Enterprise、Developer 以及两个 Enterprise 版本返回该值。） 4 = Express（对 Express、Express with Tools 和 Express with Advanced Services 返回该值） 5 = SQL Database 6 = SQL 数据仓库 8 = 托管实例 基本数据类型：int |
因为当前数据库版本为标准版，所以stated的值来自OpenRowset(TABLE DBPROP, (case when serverproperty('EngineEdition') = 5 then DB_ID() else d.id end)) p
我们可以在单用户专用连接服务器模式下查看相关记录的值。如下截图所示：
其实发现这个问题（其实我更愿意称其为一个bug）是一次查询时的意外发现。实验测试让我有点吃惊。居然这么多版本都是这种情况！ 这到底是一个“bug”还是数据库什么内部机制呢？
![【MySQL数据库】数据库索引事务1.索引2.事务[图]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)