當插入記錄時無法訪問遠程磁盤上的文件時會發生什么情況？

Question

假設我有兩個filegroups A和B database 。 filegroup B包含遠程服務器上的單個文件。

當我在filegroup B上定義的table插入記錄而遠程服務器處於脫機狀態時會發生什么？

數據庫引擎會在遠程服務器再次可用之前將所有內容存儲在 RAM 中嗎？ 會超時嗎？ 它會寫入本地磁盤上的臨時文件嗎？

需要明確的是：數據庫引擎在本地運行，但表存儲在遠程服務器上。

Answer 1

對於不涉及訪問文件存儲的任何操作，該表將是“可訪問的”。 您可以通過在 USB 驅動器上創建輔助文件組並在 USB 驅動器斷開連接時執行操作來輕松測試。

use [master]
go

create database [mysplitdb] on primary 
(name = N'FileA', filename = N'C:\SQLData\mysplitdbA.mdf'),
filegroup B
(name = 'FileB', filename = 'E:\FileB.ndf') --<-- file on usb drive
log on 
(name = N'mysplitdb_log', filename = N'C:\SQLData\mysplitdb_log.LDF')
go

use [mysplitdb]
go

create table dbo.OnSecFileGroup
(
    id int identity primary key clustered,
    col1 int,
    col2 varchar(100)
) on [B];


insert into dbo.OnSecFileGroup(col1, col2)
select top (10000) row_number() over(order by (select null)), a.name
from master.dbo.spt_values as a
cross join master.dbo.spt_values as b;

checkpoint;

select *
from dbo.OnSecFileGroup;

--remove the usb drive(abruptly)

--works, from cache
select top 500 *
from dbo.OnSecFileGroup
where id between 5000 and 6000

--works
select top 500 *
from dbo.OnSecFileGroup
where id > 9000


--insert new rows
--works (log file available, dirty pages in cache)
insert into dbo.OnSecFileGroup(col1, col2)
select top (1000) row_number() over(order by (select null)), a.name
from master.dbo.spt_values as a
cross join master.dbo.spt_values as b;

--works (log file available, table read from cache)
insert into dbo.OnSecFileGroup(col1, col2)
select top (2000) col1, col2
from dbo.OnSecFileGroup;

--works
update top(500) s
set col1 = col1+100
from dbo.OnSecFileGroup as s;


--force flush to disk
--error: 
--The operating system returned error ....
--Additional messages in the SQL Server error log and system event log may provide more detail. 
--This is a severe system-level error condition that threatens database integrity and must be corrected immediately...
checkpoint;


use master
go

--db still online
select state_desc --ONLINE
from sys.databases
where name = 'mysplitdb'

--write more rows
use mysplitdb
go
--works
insert into dbo.OnSecFileGroup(col1, col2)
select top (12000) col1, col2
from dbo.OnSecFileGroup;

--error:
--Could not allocate space for object 'dbo.OnSecFileGroup'.'PK__OnSecFil__3213E83F0425A276' in database 'mysplitdb' because the 'B' filegroup is full.
--Create disk space by deleting unneeded files, dropping objects in the filegroup ...
insert into dbo.OnSecFileGroup(col1, col2)
select top (12000) col1, col2
from dbo.OnSecFileGroup;


--connection still open
--table accessible
select top (120) col1, col2
from dbo.OnSecFileGroup
order by newid();

--stop & start sql server
use master
go

--db not online
select state_desc --RECOVERY_PENDING
from sys.databases
where name = 'mysplitdb'

--stop sql server and connect usb

--start sql server

--mysplitdb online

use master
go

--db online
select state_desc --ONLINE
from sys.databases
where name = 'mysplitdb'


--remove usb
use  mysplitdb
go

--needs access to file storage, after restart, nothing in cache
select top (120) col1, col2
from dbo.OnSecFileGroup
order by newid();

--db still online

--error..
dbcc checkdb('mysplitdb')

--cleanup
drop database mysplitdb
go