BUFFERPOOL

onconfig.std
values

UNIX Only

BUFFERPOOL default,lrus=8,buffers=5000,lru_min_dirty=50,
lru_max_dirty=60
BUFFERPOOL size=2K,buffers=5000,lrus=8,lru_min_dirty=50,
lru_max_dirty=60

End of UNIX Only

Windows Only

BUFFERPOOL default,lrus=8,buffers=2000,lru_min_dirty=50,
lru_max_dirty=60
BUFFERPOOL size=4K,buffers=2000,lrus=8,lru_min_dirty=50,
lru_max_dirty=60

End of Windows Only

syntax

BUFFERPOOL default,lrus=num_lrus,buffers=num_buffers, lru_min_dirty=percent_min,lru_max_dirty=percent_max_dirty

BUFFERPOOL size=sizeK,buffers=num_buffers, lrus=num_lrus,lru_min_dirty=percent_min, lru_max_dirty=percent_max_dirty

takes effect

When the database server is shut down and restarted

utilities

onparams -b (See Add a New Buffer Pool.)
onspaces (See Specifying a Non-Default Page Size with the Same Size as the Buffer Pool.
ON-Monitor (See Figure 31.)

refer to

Create a Dbspace or Temporary Dbspace
The IBM Informix Dynamic Server Administrator's Guide

The BUFFERPOOL configuration parameter specifies the default values for buffers and LRU queues in a buffer pool for both the default page size buffer pool and for any non-default pages size buffer pools.

The BUFFERPOOL configuration parameter consists of two lines in the onconfig.std file, as shown in this example for a UNIX platform:

BUFFERPOOL default,lrus=8,buffers=5000,lru_min_dirty=50,lru_max_dirty=60
BUFFERPOOL size=2K,buffers=5000,lrus=8,lru_min_dirty=50,lru_max_dirty=60

The top line specifies the default values that are used if you create a dbspace with a page size that does not already have a corresponding buffer pool created at start up. The line below the default line specifies the database server's default values for a buffer pool, which are based on the database server's default page size. When you add a dbspace with a different page size with the onspaces utility or when you add a new buffer pool with the onparams utility, a new line is appended to the BUFFERPOOL configuration parameter in the ONCONFIG file. The page size for each buffer pool must be a multiple of the system's default page size. Below is an example of the BUFFERPOOL lines where a third line has been appended:

BUFFERPOOL default,lrus=8,buffers=5000,lru_min_dirty=50,lru_max_dirty=60
BUFFERPOOL size=2K,buffers=5000,lrus=8,lru_min_dirty=50,lru_max_dirty=60
BUFFERPOOL size=6K,buffers=3000,lrus=8,lru_min_dirty=50,lru_max_dirty=60

The order of precedence for the BUFFERPOOL configuration parameter settings is:

1. The BUFFERPOOL size line, for example:

   BUFFERPOOL size=2K,buffers=5000,lrus=8,lru_min_dirty=50,lru_max_dirty=60

2. Any deprecated parameters in the ONCONFIG file:
   • BUFFERS
   • LRUS
   • LRU_MAX_DIRTY
   • LRU_MIN_DIRTY

   For more information about deprecated configuration parameters, see Appendix D. Discontinued Configuration Parameters.

3. The BUFFERPOOL default line, for example:

   BUFFERPOOL default,lrus=8,buffers=5000,lru_min_dirty=50,lru_max_dirty=60

4. Database server defaults.

When you use onspaces to create a new dbspace with a new page size, the database server takes the values of buffers, lrus, lru_min_dirty and lru_max_dirty from BUFFERPOOL default line unless there already is a BUFFERPOOL entry for that page size.

You can use the onparams utility when the database server is in online, quiescent, or in single-user mode to add a new buffer pool with a different page size. There must be one buffer pool for each page size used by the dbspaces and all dbspaces using that page size must use the single buffer pool with that page size. When you use the onparams utility to add a buffer pool or when you add a dbspace with a different page size with the onspaces utility, the information you specify is automatically appended to the ONCONFIG file and new values are specified using the BUFFERPOOL keyword. You cannot change the values by editing the onconfig.std file. If you need to resize or delete an existing buffer pool, you must restart the database server and then run onparams again.

Buffer pools that are added while the database server is running go into virtual memory, not into resident memory. Only those buffer pool entries that are specified in the ONCONFIG file at startup go into resident memory, depending on the availability of the memory you are using.

The fields in the BUFFERPOOL lines are not case sensitive (so you can specify lrus or Lrus or LRUS) and the fields can appear in any order.

For more information on buffer pools, including information on resizing and deleting buffer pools, see IBM Informix Dynamic Server Administrator's Guide.

The following sections explain each of the fields in the BUFFERPOOL configuration parameter.