InnoDB
Startup Options and System Variables
1239
Option-File Format
innodb_checksums
Option Sets Variable
Yes,
innodb_checksums
[1238]
Variable Name
innodb_checksums
Variable Scope
Global
Dynamic Variable
No
Permitted Values
Type
boolean
Default
ON
InnoDB
can use checksum validation on all pages read from the disk to ensure extra fault tolerance
against broken hardware or data files. This validation is enabled by default. However, under some
rare circumstances (such as when running benchmarks) this extra safety feature is unneeded and
can be disabled with
--skip-innodb_checksums
. This variable was added in MySQL 5.0.3.
•
innodb_commit_concurrency
Version Introduced
5.0.12
Command-Line Format
--innodb_commit_concurrency=#
Option-File Format
innodb_commit_concurrency
Option Sets Variable
Yes,
innodb_commit_concurrency
[1239]
Variable Name
innodb_commit_concurrency
Variable Scope
Global
Dynamic Variable
Yes
Permitted Values
Type
numeric
Default
0
Range
0 .. 1000
The number of threads that can commit at the same time. A value of 0 (the default) permits any
number of transactions to commit simultaneously. This variable was added in MySQL 5.0.12.
•
innodb_concurrency_tickets
Version Introduced
5.0.3
Command-Line Format
--innodb_concurrency_tickets=#
Option-File Format
innodb_concurrency_tickets
Option Sets Variable
Yes,
innodb_concurrency_tickets
[1239]
Variable Name
innodb_concurrency_tickets
Variable Scope
Global
Dynamic Variable
Yes
The number of threads that can enter
InnoDB
concurrently is determined by the
innodb_thread_concurrency
[1251]
variable. A thread is placed in a queue when it tries
to enter
InnoDB
if the number of threads has already reached the concurrency limit. When a
thread is permitted to enter
InnoDB
, it is given a number of “free tickets” equal to the value of
innodb_concurrency_tickets
[1239]
, and the thread can enter and leave
InnoDB
freely until it
has used up its tickets. After that point, the thread again becomes subject to the concurrency check
(and possible queuing) the next time it tries to enter
InnoDB
. The default value is 500. This variable
was added in MySQL 5.0.3.
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