本文主要向大家介绍了SQLServer数据库系统视图sys.master_files不能正确显示数据库脱机状态，通过具体的内容向大家展现，希望对大家学习SQLServer数据库有所帮助。

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(TABLEDBPROP, (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？

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