Oracle 5.0 Reference Manual page 1585

Normal read and write operations use a similar buffer, whose usage is even more short-lived.
The compile-time parameter
Dbtc/Dbtc.hpp) set to 4000 × 128 bytes (500KB). A similar buffer for key information,
ZDATABUF_FILESIZE
the module that handles transaction coordination.
Scans and buffering.
ndb/src/kernel/blocks/Dblqh/Dblqh.hpp) that affect reads and updates. These include
ZATTRINBUF_FILESIZE, set by default to 10000 × 128 bytes (1250KB) and ZDATABUF_FILE_SIZE,
set by default to 10000*16 bytes (roughly 156KB) of buffer space. To date, there have been neither any
reports from users nor any results from our own extensive tests suggesting that either of these compile-
time limits should be increased.
•
MaxNoOfConcurrentScans
Effective Version
MySQL 5.0.0
Restart Type: N
This parameter is used to control the number of parallel scans that can be performed in the
cluster. Each transaction coordinator can handle the number of parallel scans defined for this
parameter. Each scan query is performed by scanning all partitions in parallel. Each partition
scan uses a scan record in the node where the partition is located, the number of records being
the value of this parameter times the number of nodes. The cluster should be able to sustain
MaxNoOfConcurrentScans
Scans are actually performed in two cases. The first of these cases occurs when no hash or ordered
indexes exists to handle the query, in which case the query is executed by performing a full table
scan. The second case is encountered when there is no hash index to support the query but there is
an ordered index. Using the ordered index means executing a parallel range scan. The order is kept
on the local partitions only, so it is necessary to perform the index scan on all partitions.
The default value of
•
MaxNoOfLocalScans
Effective Version
MySQL 5.0.0
Restart Type: N
Specifies the number of local scan records if many scans are not fully parallelized. If the number of
local scan records is not provided, it is calculated as the product of
and the number of data nodes in the system. The minimum value is 32.
•
BatchSizePerLocalScan
Effective Version
MySQL 5.0.0
Restart Type: N
This parameter is used to calculate the number of lock records used to handle concurrent scan
operations.
MySQL Cluster Configuration Files
ZATTRBUF_FILESIZE
(also in Dbtc.hpp) contains 4000 × 16 = 62.5KB of buffer space.
There are additional
Type/Units
integer
scans concurrently from all nodes in the cluster.
MaxNoOfConcurrentScans
Type/Units
integer
Type/Units
integer
1565
(found in
ndb/src/kernel/blocks/
parameters in the
[ndbd]
Default
256
is 256. The maximum value is 500.
Default
UNDEFINED
Default
64
module (in
Dblqh
Range/Values
2 - 500
Range/Values
32 - 4G
MaxNoOfConcurrentScans
Range/Values
1 - 992
is
Dbtc