5
votes
1answer
250 views

Why are U locks required when using Read Committed Snapshot Isolation

I consider myself a beginner at Sql Server locking. My understanding is that when using RCSI, Sql Server doesn't need to issue S locks because it uses row versioning (in most cases). From ...
3
votes
1answer
101 views

Optimizing concurrent updates in Postgres

I'm running concurrent Postgres queries like this: UPDATE foo SET bar = bar + 1 WHERE baz = 1234 Each query affects the fixed K number of rows, and I can't find a way to enforce the order in which ...
0
votes
1answer
55 views

Is UDPLOCK using Row-locks?

I have a UPDATE statement that is using a UPDLOCK inside a DTCTransaction to avoid deadlocks. Now I was wondering. is it locking on a Row-level or on a Table-level?
0
votes
0answers
29 views

Why are there more MySQL deadlocks on my 8-core machine than 16-core?

I'm running a bunch of scripts in parallel that do: START TRANSACTION REPLACE INTO... REPLACE INTO... REPLACE INTO... ... COMMIT On my 8-core machine, where 8 of these processes are running in ...
2
votes
1answer
135 views

How to use proper hints for Upsert involving a top 1 subquery

For this specific case (tracking Load Balancer switches) we wish to optimize an Upsert so that it does not exhibit any race conditions, cause any PK violation, or acquire any over sized locks. ...
1
vote
1answer
362 views

How does locking work in INSERT..ON DUPLICATE KEY UPDATE statements?

I am encountering deadlocks while trying to update multiple rows (a batch) using INSERT..ON DUPLICATE KEY UPDATE. Does MySQL lock all the rows in one batch or does it lock only the row it is updating ...
0
votes
0answers
68 views

Lock timeouts on a table with two keys, where only one connection writes for a given value of the first key at a time

I have a table user_rollup_message_list that is keyed by (user_id, message_reference). It is a write-heavy table, and gets enough writes that I get many lock timeouts, with a timeout of 50 seconds, ...
2
votes
1answer
1k views

MySQL: Alter Table on very active table gives “Waiting for table metadata lock”

At my work, we've recently upgraded to MySQL 5.5 and since then, have been bitten a few times by the new (and intended) behavior of metadata locking. Basically, whenever we run an ALTER TABLE ...
2
votes
0answers
1k views

Oracle Select Query Over Database Link Suddenly Hangs Endlessly

I have a query that's been in use for years and today it started hanging endlessly. I took the query apart and found the piece causing it to hang is a simple join on a primary key that should run like ...
3
votes
1answer
715 views

Understanding SIX lock in Microsoft SQL-Server

Can somebody explain me how a process can acquire SIX lock on a page? I my deadlock-graph xml file I see that a process running under RC isolation level (executing a select statement at the moment of ...
1
vote
1answer
355 views

How can I make a select statement get blocked?

Hello I am trying to intentionally make a SQL select statement get blocked by another simple SQL delete or update statement, for the purpose of learning. I prefer only InnoDB tables. To prepare the ...
0
votes
1answer
64 views

Pessimistic locking worst case

We are using Java EE. And are making an apllication where in the worst case, aloot of message queue messages willl come form the same User. Therefore we are looking on Pessimistic, SELECT FOR UPDATE ...
3
votes
1answer
1k views

How to force the use of row locks?

I am trying to get my table to use row locks. I have already disabled lock escalation. The isolation level is READ_COMMITTED_SNAPSHOT alter table <TABLE_NAME> SET (LOCK_ESCALATION=DISABLE) go ...
4
votes
2answers
2k views

Deadlock on insert for a table with an insert trigger that updates column in same triggered table

By specification each table uses a guid as the primary key. Another requirement is that each resource requires a 6 number identifier (100001, 100002, ...) as a public id that is unique within the ...
0
votes
1answer
800 views

SQL Server 2008, database completely locked

Our database becomes completely locked, and it seems that many tables not related to each other are locked at once. When this happens, it becomes locked for approximately 2 minutes, and when this ...
3
votes
1answer
239 views

All-or-none exclusive lock on 2 SQL tables

My simplistic testing suggested that I can acquire an exclusive lock on 2 tables or postpone acquiring the lock on either until both can be acquired at once by using a query like this: SELECT ...
2
votes
2answers
403 views

Alternatives to sp_indexoption for Row Locks and Page Locks in SQL Server 2008

Are there better alternatives to setting the Row Locks and Page Locks in SQL Server 2008? The case here is to set the row and page locks to false on the table. The lock is in effect during a series ...
8
votes
2answers
456 views

How does SQL Server determine the order it takes locks in while selecting a table?

I have two stored procedures that are deadlocking when the system is under load. Proc A is selecting from a table while the Proc B is inserting into the same table. The Lock Graph is showing that Proc ...
3
votes
1answer
3k views

How to find out what caused the database(DB2) in a locking state

I know how to check the DB is in a lock state or not, but my question is how to find out which query caused the lock on table /db. IS there any log file getting created if something unexpected ...
2
votes
1answer
401 views

Locking, deadlocking workaround while process data at the same table

My database has a table: tableX. Task1 makes intensive INSERTs (1000 records per minute) as records to process and very seldom UPDATEs (1-2 records per minute) as records to recalculate. At the ...