A mechanism for managing concurrent access to shared data or resources by granting temporarily exclusive access to the processes requesting the lock.

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2answers
49 views

One of databases in MongoDB suddenly gets high lock %

I observe repeatable, sudden, short-time update queries slowdowns in MongoDB cluster for single database. That slowdowns lasts about 30 seconds and repeats few times a day. I found that lock % and ...
2
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1answer
60 views

How mysql (innodb) handles auto increment column

I am working on a OLTP environment with multiple parallel write operation. I found this in documentation about auto increment locking but still i am interested to know much about it in details. Can ...
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1answer
13 views

Sybase ASE lock table to disallow users insert values

I need to disallow users to insert values in some table, for example for a 5 mins. Seems I should use at isolation clause but can't figure out how to use it. Thanks
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1answer
59 views

MySQL 5.6 replication causes 'waiting for table lock'

All of the sudden queries on slave server stopped with status "Waiting for table level lock" I restart mysql service and stop replications and locking does not show up anymore. Once I turn ...
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1answer
166 views

How to generate replication snapshot without locking tables

When I reinitialize subscription and generate new snapshot it locks all tables and makes the database unusable for a very long time (never waited it out). Is there anyway to do this without locking?
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1answer
34 views

Is there a way to enumerate all locks that are currently being held via get_lock()?

I'm not seeing a way to list all locks currently being held by get_lock. I see you can check is_free if you know the name and release as well. I don't see an obvious function or infomration_schema ...
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1answer
500 views

InnoDB row level locks without SELECTs?

I have several (>30) MySQL clients inserting into InnoDB tables concurrently. I keep encountering lock wait timeouts and can't figure out why. Here is the situation: Each client runs the following ...
2
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0answers
303 views

How to make SSAS Commit Write take less time

We're using SQL Server Analysis Server 2012 (Enterprise) and have a process to update the cube during the day. This process is running pretty well until it gets to the final part of processing where ...
2
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0answers
2k 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 ...
2
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0answers
903 views

Insert into table from a query to a linked database hangs

I have a schema with some database links to other schemas that we use to pull data from. We pull the data into a staging table, massage it, and then do some merges into our schema/database. The data ...
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0answers
28 views

Handling this multi-threading scenario in the database?

I am working on sample bus ticket booking application,in I am facing these two multi-threading scenarios. Scenario 1 1: Let's say there are two users, they both pick a particular seat and submit ...
1
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0answers
20 views

MySQL - Transactions and causality

I'm new to MySQL's LOCK and TRANSACTION and have a question about different isolation levels of a transaction: Given two transactions executing the same code (auto-commit is false): (1) get data of ...
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0answers
37 views

Postgres advisory lock deadlocks itself?

I am executing pg_advisory_locks using the following set of statements: SELECT pg_advisory_lock(317,2); UPDATE posts SET dislikers = array_remove(dislikers, 7) WHERE id = 317; update posts set ...
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0answers
69 views

Update on a small table times out

We use Microsoft SQL Server Express Edition with Advanced Services 2008 R2 SP2 We have two locations. Each location has one sql server that serves about 20 client computers. Client computers are ...
1
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0answers
52 views

MySQL WRITE LOCK Not Preventing Inserts

This should be a simple task. Can someone tell me why the below code is still inserting rows? lock table wp_postmeta write; insert into wp_postmeta values (null, 1,'test','test'); I've checked my ...
1
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0answers
65 views

MySQL replication of single DB to same server

I have a DB Server running CentOS 6.4 and MySQL 5.5 from RPMs (not source). I have dozens of databases but one of them is being hit quite hard with large selects which locks out other updates which ...
1
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0answers
409 views

Unable to insert into or update table

A have the following table in a SQL Server 2000 database (service pack 2), with about 600,000 rows: Id [int, primary key] Form [int] Element [int] Data [char(8000)] MoreData [varchar(8000)] ...
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0answers
147 views

UPLOCK to avoid multiple reads

Given the following table structure... Orders ====== OrderId int PK OrderEvent =========== OrderEventId int PK OrderId int FK EventTypeId int FK I've got multiple concurrent processes SELECT-ing ...
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0answers
300 views

Transactional Replication Snapshots causing serious locking after 2012 upgrade

I am experiencing serious locking when adding new articles to an existing transactional replication publication, which is hanging the website. This is the first time I have attempted this since I ...
1
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0answers
287 views

Oracle locked sessions with ASP.Net

I am connecting to an Oracle database in ASP.Net using SQLDataSource. My connection string is: <add name="ConnectionString3" connectionString="Data Source=sml; User ID=sml; Password=sml; ...
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0answers
23 views

Concurrent SELECT and UPDATE in multiprocessing python

I have to randomly match about 20 million rows in two tables without using the same row twice using PostgreSQL 9.3.5. Both tables have the following structure CREATE TABLE de_sim_points_end ( -- ...
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0answers
24 views

Many transactions are getting stuck in the “cleaning up” state - what could cause that?

I'm trying to track down a locking issue, and found via SHOW PROCESSLIST that when the queries in question are waiting for locks and timing out, there are no other queries active in the process list. ...
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0answers
18 views

MySQL what is the order of the table lock for this query?

An example query looks like this: INSERT INTO Adventure (sword, fighter, quest) SELECT Swords.id, Fighters.id, Quests.id FROM swords Swords, fighters Fighters, quests Quests WHERE Swords._id = ...
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0answers
28 views

SSRS 2012 LCK_M_IX locks

I have an SSRS server running in native mode. Sometimes i see in sys.dm_exec_requests a lot of locks LCK_M_IX, which occurs while system procedures(like WriteChunkSegment, ReadChunkSegment) are ...
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0answers
36 views

How can I obtain concurrent deletes for this table?

We have a program that is currently doing something to the effect of: SET TRANSACTION ISOLATION LEVEL READ COMMITTED BEGIN TRANSACTION UPDATE [Source].[dbo].[SourceTable] SET [ProcessedOn] = ...
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0answers
53 views

MySQL Upgrade from 5.5 to 5.6 causes system / table locks

We recently upgraded from MySQL 5.5 to 5.6 on AWS RDS. Before, we had a relatively performant database - definitely had its quirks, but it seemed to be tuned relatively well. After the upgrade, we're ...
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0answers
67 views

Unresponsive MySQL database

I've setup a MySQL server on Ubuntu machine. When running a heavy query (the table has over 1M rows), the database becomes unresponsive. Upon connection it returns: Can't connect to MySQL server ...
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0answers
54 views

Rails with mysql 5.5 update queries take long

app was running Rails and MySQL 5.1 and worked quite well. When we have upgrade to the new server with MySQL 5.5 some update and delete queries started to work quite long (1 sec vs 50ms on old ...
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0answers
529 views

Why is InnoDB waiting for table metadata lock in simple INSERT/DELETE + SELECT?

I've started using a new MySQL server and moved an InnoDB table there. I'm seeing a weird behavior that when I have a long running INSERT / DELETE, any SELECT from the same table is locked which is ...
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0answers
49 views

Why does the delete/update block each other in this case?

The following drives me crazy. I have: session1>begin; session2>begin; session2>update dummy set salary=1000 where id=11; session1>delete from dummy where id=1; id is the PK ...
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0answers
31 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 ...
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0answers
54 views

MySQL Multiple threads inserting *SAME* record a Bad Thing?

Okay, as I've noted in other questions, I'm not a sophisticated database user even though I took my first course in relational algebra from ted Codd. I've now inherited an application that ...
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0answers
80 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, ...
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0answers
99 views

What would this non-'unique index with a unique search condition` query lock?

I am not sure about this part of the transaction manual For locking reads (SELECT with FOR UPDATE or LOCK IN SHARE MODE), UPDATE, and DELETE statements, locking depends on whether the statement ...
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0answers
83 views

Which mysql server 5.5 variables would be involved in queries locking in sending data state?

A large portion of my queries (~58%) be it for queries with previously quick return rates or other, are spending in my monitor as sending data. I made some configuration changes but it was very broad ...
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0answers
101 views

Being careful about additional records being added in a duplicate record merge?

We have a multi-user MS-Access 2003 database. Connecting to it using SQuirrel SQL, and the JDBC/ODBC bridge, I've managed to eek transactions of some sort out of JET by turning off autocommit. I've ...