| Measurement |
Description |
Measurement
Unit |
Interpretation |
| Cache_hit_rate |
The percentage of successful accesses to the data cache |
Percent
|
A high hit rate of at least 98% is recommended for the data cache. If the hit rate is low, consider changing the size of the data cache.
|
| Cache_usable_size |
The current size of the data cache |
MB
|
The size of the data cache has the following effect on the performance of the database system:
- A large data cache makes a high hit rate possible.
- If the data cache is too large for a small main memory, this can lead to operating system swapping with a very high level of I/O activity.
However, since the data cache is dynamically dimensioned by the database system, you cannot configure the size of the data cache directly, but can only influence it implicitly by configuring the I/O buffer cache. The database system takes the pages required for the data cache from the I/O buffer cache. If the other I/O buffer cache user, the converter, grows in size, the database system decreases the size of the data cache, if necessary.
|
| Cache_used_size |
The currently utilized portion of the data cache |
MB
|
If converter cache or catalog cache run out of space, the data cache is used; so, it is recommended that you increase the overall cache size.
|
| Pct_cache_used |
The percentage of the cache that is utilized |
Percent
|
If converter cache or catalog cache run out of space, the data cache is used; so, it is recommended that you increase the overall cache size. |
| Oms_data_size |
The size of the data cache that is currently used for storing OMS data |
MB
|
Since the data in an SAP liveCache database instance consists mainly of OMS data, you should configure the data cache for SAP liveCache database instances to be large enough to store all the OMS data, if possible. |
| History_data_size |
The size of the data cache required for consistent reads and transactions management
|
MB
|
|
| Sql_data_size |
The size of the data cache not required either for OMS data or consistent reads and transaction management
|
MB
|
|