locking

I've got a stored procedure, which selects 1 record back. the stored procedure could be called from several different applications on different PCs. The idea is that the stored procedure brings back the next record that needs to be processed, and if two applications call the stored proc at the same time, the same record should not be brought back. My query is below, I'm trying to write the query as efficiently as possible (sql 2008). Can it get done more efficiently than this? CREATE PROCEDURE GetNextUnprocessedRecord AS BEGIN SET NOCOUNT ON; --ID of record we want to select back DECLARE @iID

I need to open a file but if it's currently not available I need to wait until it's ready. What's the best approach to take? SCENARIO I'm using files as a persistent caching mechanism for application data. This data needs to be read and deserialized often (written only once, and deleted occasionally). I have a cleanup process that runs on a separate thread that determines which files are no longer needed and deletes them. Opening and reading of files may happen concurrently (rarely, but could happen) and I want the process to wait and try to read the data again. Thanks! csharptest.net I'm not

Is there a way to lock a row in the SQL 2005-2008 database without starting a transaction, so other processes cannot update the row until it is unlocked? You can use RowLock or other hints but you should be careful .. The HOLDLOCK hint will instruct SQL Server to hold the lock until you commit the transaction. The ROWLOCK hint will lock only this record and not issue a page or table lock. The lock will also be released if you close your connection or it times out. I'd be VERY careful doing this since it will stop any SELECT statements that hit this row dead in their tracks. SQL Server has

I've read a lot of examples on locking threads.. but why should you lock them? From my understanding, when you initiate threads without joining them, they will compete with the main thread and all other threads for resources and then execute, sometimes simultaneously, sometimes not. Does locking ensure that threads DON'T execute simultaneously? Also, what wrong with threads executing simultaneous? Isn't that even better? (faster overall execution) When you lock threads, will it lock them all or can you choose which ones you want to be locked? (Whatever locking actually does...) I'm referring

I have a stored procedure in mysql thats to perform a task that needs to be synchronized such that if two application calls the stored procedure, only one can access a section of code to perform the task, keeping the other one to get blocked until the first one finishes the task. DELIMITER $$ CREATE PROCEDURE SP_GEN_ID(IN NAME VARCHAR(20)) BEGIN DECLARE maxLen int default 0; START TRANSACTION; #the section of code that needs to be synchronized COMMIT END; $$ DELIMITER ; So, if two applications call the stored procedure simultaneously, the task has to be synchronized. a. But Start TRANSACTION

I learned that calling an Object's wait() method will release the object monitor, if present. But I have some questions regarding calling notify() on this object by another thread: (when) will the waiting thread wake up, if another (a 3rd) thread owns the object monitor in the meanwhile? will the waiting thread wake up, if a 3rd thread called wait() on this object? is it possible to determine if a thread is waiting for notifying a particular object (java 1.4/java 5) What's happening if wait() will be called in the finalize() method? notify will wake one thread waiting on the monitor. Unless