|Table 5. Performance Variables
Variable Name | Operating System | Values |
---|---|---|
Description | ||
DB2_BLOCK_BASED_BP | Solaris | Default=None
Values: dependant on parameters |
Specifies the
values needed to create a block area within a buffer pool. The ID of the buffer
pool is needed and can be seen in the BUFFERPOOLID column of the SYSCAT.BUFFERPOOLS
system catalog view. The number of pages to be allocated in the buffer pool
to block-based I/O must be given. The number of pages to include in
a block is optional, with a default value of 32.
The format for the use of this registry variable is:
DB2_BLOCK_BASED_BP=BUFFER POOL ID,BLOCK AREA SIZE,[BLOCK SIZE];...
Multiple buffer pools can be defined as block-based using the same variable with a semi-colon separating the entries.
The value for BLOCK SIZE can range from 2 to 256. If no BLOCK SIZE is given, the default used is 32.
If the BLOCK AREA SIZE specified is larger than 98% of the total buffer pool size, then the buffer pool will not be made block-based. It is a good idea to always have some portion of the buffer pool in the page-based area of the buffer pool because there is a possibility of individual pages being required even if the majority of the I/O on the system is sequential prefetching. If the value specified for BLOCK AREA SIZE is not a multiple of BLOCK SIZE, it is reduced to the nearest block size boundary. For more information on block-based I/O, see 9.2.1, Block- Based Buffer Pool. | ||
DB2_NO_FORK_CHECK | UNIX | Default=OFF
Values: ON or OFF |
When this variable is "ON", the client process will not protect itself against an application making a copy of the process to be run (called forking). When forking occurs, the results are unpredictable. The results could range from no effect, to some bad results, to some error code being returned, to a trap in the application. If you are certain that your application does not fork and you want better performance, you should change the value of this variable to "ON". |
|The DB2_NEWLOGPATH2 registry variable is available for all operating systems. A new variable, DB2_ROLLFORWARD_NORETRIEVE,
|has been introduced. The correct information for both variables appears below.
|
|Table 6. Miscellaneous Variables
|A new variable, DB2_REDUCED_OPTIMIZATION, has been introduced.
|
|Table 7. General Registry Variable
Variable Name | Operating System | Values |
---|---|---|
Description | ||
DB2_REDUCED_OPTIMIZATION | ALL | Default=NO
Values: YES, NO, or any integer |
This registry
variable lets you disable some of the optimization techniques used at specific
optimization levels. If you reduce the number of optimization techniques
used, you also reduce time and resource use during optimization.
Note that the dynamic optimization reduction at optimization level 5, as described in "Adjusting the Optimization Class" in Administration Guide: Performance, takes precedence over the behavior described for optimization level of exactly 5 when DB2_REDUCED_OPTIMIZATION is set to YES as well as over the behavior described for the integer setting. |