Monitoring the Main Memory Areas 

A liveCache database instance can work at an optimized level if the liveCache data is accessed in the main memory only. Avoid accessing the data in the data area.

For this reason, when you analyze liveCache performance, first analyze the main memory areas data cache and OMS heap.

Prerequisites

When you start a liveCache database instance, the data cache and converter are dimensioned as specified by the database parameter CACHE_SIZE.

The size of the OMS heap is undefined when liveCache database instance is started. The OMS heap can grow dynamically until it reaches the maximum size specified in the liveCache parameter OMS_HEAP_LIMIT.

Monitoring the Data Cache

The memory of the data cache should take up about 40% of the main memory available to a liveCache database instance. You may need to adjust its size to the requirements of the application.

Among other things, the following data is stored in the data cache:

·        OMS Data

See: OMS

·        Links to Undo Log Entries

See also: History Management

·        SQL Data

This data is organized in database tables and, if required, indexes like an OLTP database system. The data is managed in SQL data pages in the form of B* trees which, among other things, contain the following data: the object key, the database tables and their indexes and the OMS-Version for any swapping activities. Usually, only about 2-3% of the total data cache is used for SQL data.

The data cache must be dimensioned so that it can hold all OMD data, links to Undo Log Information and SQL data in the data cache. Otherwise, the data is written to the data area, which negatively affects the performance of the liveCache database instance. This should hardly ever occur.

·        The data cache hit rate should be at least 99.8%.

·        The data cache load should be significantly less than 100%.

·        The amount of OMS data in the data cache should be significantly higher than the amount of links to Undo Log Entries (a ratio of 4:1 is normal).

To monitor the Data Cache, you can use the Caches   display in the liveCache Assistant or the display in liveCache Alert Monitor Caches and Memory.

Critical Situations

·        The data cache hit rate is below 99.8%, the data cache load is 100%.
To display the failed accesses to the data cache, refresh the Caches display in the liveCache Assistant.
Check whether there are any long-running OMD versions.
If the measures described here do not improve the critical situation, increase the dimensions of the data cache.

·        The amount of OMS data and Undo Log Entries is about the same or there is more Undo Log Entries than OMS data.
Check the OMS versions that generated the Undo Log Entries.
Proceed as described in Monitoring OMS Versions.

Monitoring the OMS Heap

To monitor the OMS heap, use the heap consumption display in the liveCache Assistant or the Memory display in liveCache Alert Monitor.

Critical Situations

·        The filling level of the OMS heap is greater than 80 %.
Proceed as described in Monitoring OMS Versions.

·        The filling level of the OMS heap is greater than 90%.
DB procedures usually terminate if the OMS heap has almost reached its maximum value.
- You can reduce the size of the data cache ( general database parameter CACHE_SIZE) and increase the OMS heap ( liveCache parameter OMS_HEAP_LIMIT) instead.
- You can make more main memory available to increase the size of the OMS heap (liveCache parameter OMS_HEAP_LIMIT).