CMS Snapshot Analysis - Run Analyzer - Information - Understand AMT traces
Purpose
Follow the below steps which will describe different aspects of AMT memory log. It will help you identify possible out-of-memory issues.
List of Analyzers for which we need AMT traces : CMS Snapshot Analysis - Run Analyzer - Information - How to enable memory traces
Applicable in CAST Version
| Release | Yes/No |
|---|---|
| 8.3.x | ✅ |
Applicable RDBMS
| RDBMS | Yes/No |
|---|---|
| CSS | ✅ |
Details
How to understand the information in AMT log
CAST alloc Bytes : Represents memory used by the analyzer.
CAST res bytes : Represents the memory used by the cast allocator.
System free virt Bytes : The amount of virtual memory currently available, in bytes. This is the amount of RAM that can be immediately reused.
System free phys Bytes : The amount of physical memory currently available, in bytes. This is the amount of physical memory that can be immediately reused without having to write its contents to disk first. It is the sum of the size of the standby, free, and zero lists.
In the below example, we have exceeded the standard 32 Bits Memory Threshold : 1.8 Gb, this is an Out Of Memory issue.
Get the analysis log as well as the AMT traces. The timestamp on both files must be from the same period of time.
Figure 2
Read the System free virt Bytes and System free phys Bytes. The value of System free virt Bytes must be higher than 100 MB and System free phys Bytes must be higher than 200 MB. If one of the two values is smaller than this limit, then the analyzer is running out of memory. If not, the analyzer is not running out of memory.
When the option “Activate AMT Memory Profiling” is enabled
- If the AMT_memory.log file does not exist, the analysis will create it.
- Each new run will add traces on the existing AMT_memory.log file.
- To avoid any crash due to the size of the file that can lead to a lack of disk space, before the run analysis, you must delete the AMT_memory.log file, if the content of the trace are not required or if they are too old.
Sample AMT log file
Notes/comments