Question

SQL Server is SQL Azure, basically it’s SQL Server 2008 for normal process.

I have a table, called TASK, constantly have new data in (new task), and removed (task complete)

For new data in, I use INSERT INTO .. SELECT ..., most of time takes very long, lets say dozen of minutes.

For old data out, I first use SELECT (WITH NOLOCK) to get task, UPDATE to let other thread know this task already starts to process, then DELETE once finished.

Dead lock sometime happens on SELECT, most time happens on UPDATE and DELETE.

this is not time critical task, so I can start process the new data once all INSERT finished. Is there any kind of LOCK to ask SELECT not to select it before the INSERT finished? Or any kind of other suggestion to avoid Conflict. I can redesign table if needed.

Answer 1

later the sqlserver2005,resolve lock is easy.
for conflict
1.you can use the service broker.
2.use the isolution level.

dbcc useroptions ,at last row ,you can see the deflaut isolution level is read_committed,this is the session level.
we can change the level to read_committed_snapshot for conflict,in sqlserver, not realy row lock like oracle.but we can use this method implement.

ALTER DATABASE DBName
SET READ_COMMITTED_SNAPSHOT ON;

open this feature,must in single user schame.

and you can test it.
for session A ,session B.

A:update table1 set name = ‘new’ with(Xlock) where id = 1
B:you still update other row and select all the data from table.

my english is not very good,but for lock ,i know.

in sqlserver,for function ,there are three locks.
1.optimistic lock ,use the timestamp(rowversion) control.
2.pessimism lock ,force lock when use the date.use Ulock,Xlock and so on.
3.virtual lock,use the proc getapplock().

if you need lock schame in system architecture,please me email : [e-mail]