Sun Java System Application Server Enterprise Edition 8.1 2005Q2 High Availability Administration Guide

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### Data Buffer Pool Information

Data buffer pool information contains the following:

- `NodeNo`: Node number.

- `Avail`: Total space available in the pool, in MBytes.

- `Free`: Free space available, in MBytes.

- `Access`: Cumulative number of accesses to the data buffer from database, from start until now.

- `Misses`: Cumulative number of page faults that have occurred from database start until now.

- `Copy-on-Write`: Cumulative number of pages copied internally in the data buffer due to checkpointing.

When a user transaction performs an operation on a record, the page containing the record must be in the data buffer pool. If it is not, a `miss` or a page fault occurs. The transaction then has to wait until the page is retrieved from the data device file on the disk.

If the miss rate is high, increase the data buffer pool. Since the misses are cumulative, run `hadbm resourceinfo` periodically and use the difference between two runs to see the trend of miss rate. Do not be concerned if free space is very small, since the checkpointing mechanism will make new blocks available.

##### Example 3–17 Example data buffer pool information

For example:

    NodeNO Avail Free Access Misses Copy-on-Write
    0 256 128 100000 50000 10001 256 128 110000 45000 950

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