How GoldenGate process consumes memory

Question:
We are using Golden Gate to replicate the data from Oracle 9.2.0.8 on Solaris8 SPARC 64 bit (GoldenGate Version 10.4.0.31 Build 001) to Oracle RAC 11.2.0.1 on Solaris10 SPARC 64bit (GoldenGate Version 10.4.0.19 Build 002). Both GoldenGate Extract and Replicat process are working fine. Please refer below information for more easy to understand our goldengate setup.

Extract Side | Replicat Side
Hostname: HK8SN020 | Hostname: HK8SP226 (HK8SP227 dont have any goldengate client, all goldengate process are located on HK8SP226)
Oracle 9.2.0.8 (32bit binary) | Oracle 11.2.0.1 (64bit binary)
Solaris8 Sparc 64bit Kernel | Solaris10 Sparc 64bit kernel
GoldenGate Version 10.4.0.31 Build 001 | GoldenGate Version 10.4.0.19 Build 002

However, on 27-Mar-2010, we found the server memory utilization on Solaris10 HK8SP226 are unexpected continuously rising since around 01:30. At around 3:20, the server memory utilization are up to 100%. At around 5:20, the server memory utilization is suddenly drop and back to normal. We compared the “Sar -r” and Solaris server message logfile. We found that on 05:21:44, goldengate relicate process are terminated with error message ” malloc 2097152 bytes failed”. After that, seem the server memory are suddenly released and back to normal memory utilization level.
We suspected the abnormal server memory usage are cased by goldengate replicate process. Can you please help to investigate and find out the root cause?

Answer:
GoldenGate replicates only committed transactions, it stores the operations of each transaction in a managed virtual-memory pool known as a cache until it receives either a commit or a rollback for that transaction. One global cache operates as a shared resource of an Extract process. The following sub-pools of virtual memory are allocated from the global cache:(1)One sub-pool per log reader thread for most transaction row data. and (2)One sub-pool for BLOB data and possibly other large items.

Within each sub-pool, individual buffers are allocated from the global cache, each one containing information that is relative to a transaction that is being processed by GoldenGate. The sizes of the initial and incremental buffers are controlled by the CACHEBUFFERSIZE option of CACHEMGR.

The actual amount of physical memory that is used by any GoldenGate process is controlled by the operating system, not the GoldenGate process. The global cache size is controlled by the CACHESIZE option of CACHEMGR.Cache manager keeps a GoldenGate process working within the soft limit of its global cache size, only allocating virtual memory (not physical memory) on demand. The actual amount of physical memory that is used by any GoldenGate process is controlled by the operating system, not the GoldenGate program.

GoldenGate cache manager only takes advantage of the memory management functions of the operating system to ensure that GoldenGate processes work in a sustained and efficient manner. Within cache, OGG makes use of all the modern “virtual memory” techniques by allocating and managing active buffers efficiently and recycling old buffers instead of paging to disk, when possible and paging less-used information to disk, when necessary.

When COM initializes, by default it first determines how much virtual memory the OS has available for it and uses that to determine what CACHESIZE should be. Default for CACHESIZE is 8GB for 64-bit systems and 2GB for 32-bit systems.

The available virtual memory is reported with the PROCESS VM AVAIL FROM OS value in the report file. The CACHESIZE value will either be rejected or sized down if it is larger than, or sufficiently close to, the amount of virtual memory that is available to the process.

The CACHESIZE value will always be a power of two, rounded down from the value of PROCESS VM AVAIL FROM OS, unless the latter is itself a power of two, in which case it is halved. After the specified size is consumed by data, the memory manager will try to free up memory by paging data to disk or by reusing aged buffers, before requesting more memory from the system.

The memory manager generates statistics that can be viewed with the SEND EXTRACT or SEND REPLICAT command when used with the CACHEMANAGER option.The statistics show the size of the memory pool, the paging frequency, the size of the transactions, and other information that creates a system profile. Based on this profile, you might need to make adjustments to the memory cache if you see performance problems that appear to be related to file caching. The first step is to modify the CACHESIZE and CACHEPAGEOUTSIZE parameters. You might need to use a higher or lower cache size, a higher or lower page size, or a combination of both, based on the size and type of transactions that are being generated. You might also need to adjust the initial memory allocation with the CACHEBUFFERSIZE option. It is possible, however, that operating system constraints could limit the effect of modifying any components of the CACHEMGR parameter. In particular, if the operating system has a small per-process virtual memory limit, it will force more file caching, regardless of the CACHEMGR configuration.

Once the CACHESIZE is set to 1 GB, the GoldenGate process will use up to 1 GB virtual memory and then it will use swap space on disk.
If the CACHESIZE is explicitly set in process parameter file then the CACHEMGR will use only 1GB. Otherwise it will default to the Memory size depending upon the platform(32 or 64).If a fixed CACHESIZE is set in the parameter file then it will be taken by the process, if no the default will be taken by the process depending upon the platform. If very low virtual memory limit is set or available in the OS then it will force more file caching. There is always a difference between caching in memory buffers and file caching as it involves read and write i/o’s.

So try to set a default CACHESIZE for the GoldenGate Process (Extract/Replicat). Edit the respective source extract and target replicat parameter files and use the below mentioned CACHEMGR parameter with the options given and restart the processes.

CACHEMGR CACHEBUFFERSIZE 64KB, CACHESIZE 1GB, CACHEDIRECTORY
, CACHEDIRECTORY
Example:
CACHEMGR CACHEBUFFERSIZE 64KB, CACHESIZE 1GB, CACHEDIRECTORY /ggs/dirtmp, CACHEDIRECTORY /ggs2/temp

So once the CACHESIZE is set to 1 GB, the GoldenGate process will use up to 1 GB virtual memory only and then after it will use swap space on disk.

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