Indicates the number of data pages read in from the table
space containers (physical) by asynchronous engine dispatchable units
(EDUs) for all types of table spaces.
Table 2. Snapshot Monitoring InformationSnapshot Level |
Logical Data Grouping |
Monitor Switch |
Database |
dbase |
Buffer Pool |
Table Space |
tablespace |
Buffer Pool |
Buffer Pool |
bufferpool |
Buffer Pool |
For snapshot monitoring, this counter can be reset.
Table 3. Event Monitoring InformationEvent Type |
Logical Data Grouping |
Monitor Switch |
Database |
event_db |
- |
Tablespaces |
event_tablespace |
- |
Usage
You
can use this element with
pool_data_p_reads to
calculate the number of physical reads that were performed synchronously
(that is, physical data page reads that were performed by
database
manager agents).
Use the following formula to calculate the number of synchronous data
reads:
# of sync data reads = pool_data_p_reads + pool_temp_data_p_reads - pool_async_data_reads
By comparing the ratio of asynchronous
to synchronous reads, you can gain insight into how well the prefetchers
are working. This element can be helpful when you are tuning the
num_ioservers configuration
parameter. You can calculate the ratio of asynchronous reads to synchronous
reads by using the following formula:
1-((pool_data_p_reads + pool_index_p_reads)-(pool_async_data_reads + pool_async_index_reads))/(pool_data_l_reads+pool_index_l_reads)
Asynchronous reads are performed by database
manager prefetchers.