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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1answer
892 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?
1
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0answers
32 views

Row locks on selects

select t.*, row_number() over ( partition by t.Entity_Identifier order by t.Message_Sequence ) as seqnum from Process_Activity t (ROWLOCK) where t.Process_Id = Is it possible for ...
0
votes
1answer
250 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 ...
-2
votes
0answers
14 views

Scavenger hunt on quest for knowledge led me to SST table keys hash failure and databases [closed]

My adventure started with a bootloader that would not re-Lock on my friends nexus 6. Through my investigating and research I think that the issue may be at a deeper level into the code. My original ...
0
votes
2answers
1k views

Lock wait timeout exceeded on insert despite low lock_time in the slow query log

Our Java/Spring application reports occasional lock wait timeouts on single record INSERTs to a MySQL 5.5 InnoDB table. Here are a few slow query log records for some of the failed INSERTs. # ...
0
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1answer
212 views

MySQL: SELECT GET_LOCK slow/timeout

I am using "Zebra Session" as a replacement for PHP's built-in session management. Zebra Session stores sessions in a MySQL database, and uses "session locking" in order to ensure that data is ...
3
votes
1answer
141 views

Work queue with complex select and long processing: Ensuring concurrency

I have a queue table from which worker processes claim records, one at a time. It is crucial that no two workers claim same item to process. Normally this kind of thing is done with select top (1) ...
1
vote
1answer
121 views

SELECT RELEASE_LOCK causing “Mysql has gone away”

During a long running process (90m+), our code calls SELECT RELEASE_LOCK('..');. However it always gives a "Mysql has gone away" error when we do this. We have tried a number of things including ...
1
vote
1answer
100 views

Will insert and update wait while a table is being vacuumed?

I want to vacuum a table in PostgreSQL version 9.1 which will take between 10 to 12 minutes. This needs to be done in real-time, in production use. I just want to know that if any INSERT or UPDATE ...
0
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1answer
205 views

How to update a (very) large table without locking in MySQL

I have a large table (58+ million records) which represents a relation between two records (player and target) in a second table. Unfortunately, whoever designed our schema didn't think things ...
1
vote
1answer
408 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 ...
0
votes
1answer
150 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
3
votes
1answer
43 views

Locking in Postgres for UPDATE / INSERT combination

I have two tables. One is a log table; another contains, essentially, coupon codes that can only be used once. The user needs to be able to redeem a coupon, which will insert a row into the log table ...
0
votes
1answer
23 views

MySql Lock Tables Blocking Logic

The MySQL documentation (5.5) for Lock tables states: Let's say that I'm trying to lock table1 and table2 in a single query, but table2 is already locked. Will MySQL hold onto a lock on table1 and ...
1
vote
2answers
158 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
votes
1answer
1k 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 ...
2
votes
2answers
55 views

Locking issues under transaction on Postgres

I recently got a "Out of shared memory - You might need to increase max_locks_per_transaction" error. This is a long running process where I import a bunch of CSV files after proper processing. I ...
1
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0answers
50 views

Why are SELECT queries in sleeping status holding open transactions

Using sp_WhoIsActive, I see that I have a lot of processes in a "sleeping" status, several for hours. I am not sure of the cause and am still troubleshooting (timeout? bad code with uncommitted ...
0
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0answers
72 views

MySQL queries waiting for table lock

Today I had some weird behaviour on my MySQL server that I couldn't explain. Hopefully someone can give me some debugging hints. The initial problem was that some parts of our webshop didn't seem to ...
1
vote
1answer
70 views

INSERT [TableName] SELECT * FROM [TableName]

I just ran across a query: INSERT [TableName] SELECT * FROM [TableName] Note that it is the same table. This query causes serious blocking on one of my test databases (I wanted to drop it but ...
2
votes
0answers
41 views

innodb update with limit locks all matching (ignores limit)

For a query similar to this: UPDATE myinnotable1 SET value=5,updated=now(),status=1 WHERE status>10 AND message="match msg" LIMIT 1; I found that innodb engine locks ALL rows matching criteria ...
2
votes
0answers
51 views

Why does SQL Server 2005 only use an IS lock in this scenario?

I am attempting to examine the locking behind different queries but with the same output to avoid deadlocking situations. I have the following code: SELECT MIN(ID), TextData FROM PKKEYTESTER ...
2
votes
2answers
49 views

Blocked Process Report -two updates causing a long block

I have a .NET application which is getting SQL update timeouts and I believe that some sort of blocking/locking is taking place which is causing this. I have ran a blocking process report on the ...
1
vote
1answer
37 views

Viewing Type Of Lock Being Used T-SQL - Update Lock Query Issue

I am looking for a way to determine whether SQL will take a shared lock or an update lock. Take these three queries. I believe in that in theory: Query one will take a shared lock on the pk, due ...
2
votes
1answer
42 views

Create Database and LCK_M_S

We are experiencing issues when creating a database in the SSMS GUI in that sometimes it times out complaining that it could not get an exclusive lock on the Model database. Other times the database ...
1
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2answers
1k views

How to avoid locks by large transactions?

We have a large application running, that requires cleanup for performance reasons. This was however not forseen when designing the application. Basically, the delete is executed from a stored ...
3
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0answers
48 views

In Sql Server, is there a way to check if a selected group of rows are locked or not?

We are attempting to update/delete a large number of records in a multi-billion row table. Since this is a popular table, there is a lot of activity in different sections of this table. Any large ...
0
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0answers
24 views

Trigger copies history table: Will removing index lock options speed up the process?

I have a trigger applied to a table to write inserts and updates to a history table. That history table can grow pretty fast, and we want to see, if we can speed up insert operation a bit. The values ...
1
vote
1answer
44 views

How does the table scan in an UPDATE WHERE predicated on an unindexed column work?

I was looking into a deadlock caused by two concurrent UPDATE statements: UPDATE [table] SET [column] = 0 WHERE [unindexed_column] = @id My understanding is that because the column the WHERE is ...
2
votes
1answer
198 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 ...
6
votes
5answers
6k views

Can I be automatically notified of prolonged blocking in SQL server?

About once a week I have to resolve a blocking chain on a SQL Server 2005 database, caused by a long-lived read lock from an Access 2003 front-end. The lock is taken out whenever a user opens a ...
5
votes
4answers
162 views

View locks acquired during query execution (SQL Server)

Query execution plan does not show the locking details by default, is it possible to view the locks, along with the type, acquired during the execution of a query?
2
votes
1answer
1k views

MySQL : “FLUSH TABLES WITH READ LOCK” started automatically

I would like to understand how this happened. I was running a query that would take a long time, but should not lock up any table. However, my dbs were practically down - it seems like it was being ...
3
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1answer
79 views

Lock in mysql database

My schema 'test' has 3 tables: 'user', 'post' and 'revision'. CREATE TABLE IF NOT EXISTS `test`.`user` ( `iduser` INT UNSIGNED NOT NULL AUTO_INCREMENT, `name` VARCHAR(45) NOT NULL, PRIMARY KEY ...
3
votes
2answers
273 views

Performance hickups after Postgres 9.4 upgrade

After upgrading our database from 9.3.5 to 9.4.1 last night, the server suffers from high CPU spikes. The upgrade was done with pg_dump. So the database was converted to SQL and then imported into ...
4
votes
0answers
17 views

Lock in mysql database [duplicate]

My schema 'test' has 3 tables: 'user', 'post' and 'revision'. CREATE TABLE IF NOT EXISTS `test`.`user` ( `iduser` INT UNSIGNED NOT NULL AUTO_INCREMENT, `name` VARCHAR(45) NOT NULL, PRIMARY KEY ...
0
votes
1answer
33 views

How does PostgreSQL decide which query to cancel during deadlock cleanup

I know that PostgreSQL will detect and clear deadlock once it happen by cancelling one of the queries. How does PostgreSQL decide which one to cancel? Is this deterministic or there is some randomness ...
0
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1answer
74 views

Rolling update to all rows in innodb table (no rollback if aborted)

I have the following table, which stores the Social Security Death Master File database (~86M rows): CREATE TABLE `death_master_files` ( `id` int(11) NOT NULL AUTO_INCREMENT, `ssn_an` smallint(5) ...
6
votes
2answers
9k views

When a record is locked in Oracle, can we know which record is locked?

When a record is locked ,can we know which one is locked? How can I get the record rowid or something else info? I can get some info by this sql SELECT ...
2
votes
1answer
40 views

Implications of setting READ_Write

I am looking to update several users on READ_ONLY databases. As the databases are used 24/7 globally, and maintenance windows have just past, I would like to do this during a low-activity moment (to ...
0
votes
1answer
25 views

I have a DB that is locking up from numerous updates to a table: Should I convert it from MyISAM to InnoDB?

FYI: I don't believe this is a duplicate question, I've looked and most are general questions with vague answers. See more specifics below: Currently a database I am in charge of locks up every once ...
0
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0answers
54 views

Postgresql: Update or insert stuck

I'm running update-or-insert query on a table of approximatelly 3mln rows, 4 columns. Query is part of every day process, and for same days, the query stucks forever. It's just blocked. It's ...
2
votes
2answers
110 views

mysql write lock

I dont add any manual locking or any transaction anything, just manual running queries from php script, and execute below two update queries at the same time update table_x set status = 'PROCESSING' ...
1
vote
1answer
56 views

Deadlock scenario, where is this S lock coming from?

I am encountering the below deadlock scenario. Please see the attached object definitions and execution plans. The plans were pulled out of cache from a system where this deadlock does occur. I ...
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votes
4answers
52k views

How to determine if an Oracle table is locked or not?

We've been using BI software and a repository database that are installed on Oracle Enterprise 11gR2. Some of these batch reports will try to access a database table which may still be locked. How ...
3
votes
1answer
131 views

How to perform server-side transaction timeout if COMMIT TRANSACTION will never arrive?

How can SQL Server terminate one of its transactions if it exceeds preset timeout? Imagine the following transaction performed by traveling salesman's SQL client application, which is submitted ...
0
votes
1answer
188 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 ( -- ...
2
votes
0answers
44 views

SQL Server 2008 R2 - Should I be worried at this statistics regarding indices causing locks?

We have some mild table locking issue during our peak hours so I figured the following query query taken from this site would be a good start. And boy, does it show me some seriously concerning ...
3
votes
4answers
7k views

Why is optimistic locking faster than pessimistic locking?

Both forms of locking cause a process to wait for a correct copy of the record if its currently in use by another process. With pessimistic locking, the lock mechanism comes from the DB itself (a ...
2
votes
2answers
209 views

Is it safe to cancel a PostgreSQL ALTER TABLE query that is waiting on a lock?

We started an ALTER TABLE query hours ago and only recently realized (via pg_stat_activity) that it is waiting on a lock. We discovered the other query that is holding a lock on the table we want to ...