After the MOT transaction in the openGauss database is complete, the local memory is not released. How can I find the cause?
OpenGauss provides two functions to check the memory usage of MOT transactions. You are advised to use the function to query:
mot_session_memory_detail(): checks the MOT memory usage of all sessions.
mot_local_memory_detail(): checks the size of the MOT local memory, including data and indexes.
thanks
Related
the Memory-Optimized-Table for openGauss is purely in-memory table? or it's can persist the data when data is larger that the server memory? or at least persist when server shutdown?
MOT storage engine is a pure in-memory engine, so yes the whole data must fit into the memory. But MOT tables are strictly durable with persistence capabilities (redo log and checkpoint).
The Memory-Optimized-Table for openGauss is an memory table.When the total memory usage is close to the selected memory limit.MOT no longer allows additional data to be inserted.But It can also persist data when the server is shut down(persistence capabilities).
In the openGauss database, data is inserted into the MOT table but is not submitted. When the mot_global_memory_detail() is used to check the global memory, the global memory keeps increasing. Why?
Inserts will use global memory for rows and index keys, if you rollback the transaction the memory will be released back. That's the reason why you see global memory increasing even though the transaction is not committed yet.
Out of Memory Error
ORA -04030: Out Of Process Memory When Trying to allocate 64528 byte(Short subheap, sort key)
Generally speaking this is an actual out of memory error on the Oracle server typically caused by a too small pga.
The most likely resolution (depending on your server version) in to increase the PGA_AGGREGATE_TARGET configuration setting.
We would like to keep primary keys in memory and backup keys on disks. So on re-shuffle, we will accept the performance of reading key/values from disks.
From my research on the ignite documentation, I don't see that option out of the box. Is there any way to do this via configuration?
If this feature doesn't exist, as a workaround I had the following idea. If we know our cache takes 1 terabyte, we know with backups it will be 2 terabytes. (Approximately) If we allocate a little over 1 terabyte in memory and set the eviction policy to disk, will this effectively get us the functionality we want? That is, will it evict backup copies to disk and leave primaries in memory?
This feature doesn't exist and your workaround won't work because it will randomly evict primary and backup copies. However, you can probably implement your own eviction policy that will immediately evict any created backup and configure swap space to store this backups.
Note that I see sense only in case you're running SQL queries and/or if you don't have persistence store. If you only use key based access, any lost entry will be reloaded from the persistence store when needed.
I've got Oracle database that is used as a storage for web services. Most of the time data are in read-only mode and cached in RAM directly by the service. However during the system startup all data are pulled once from Oracle and the database tries to be smart and keeps the data in RAM (1GB).
How can I limit/control the amount of RAM available to the Oracle 9 instance?
A short answer is modify SGA_MAX_SIZE. The long one follows.
If you are referring to the "data", you have to check the DB_CACHE_SIZE (size of the memory buffers) and related to this the SGA_MAX_SIZE (max memory usage for the SGA instance).
Because SGA_MAX_SIZE reffers to the SGA memory (buffers, shared pool and redo buffers) if you want to free up the size of buffers you also have to drecrease the SGA_MAX_SIZE.
Take a look to Setting Initialization Parameters that Affect the Size of the SGA or give more details.
There are several database parameters that control memory usage in Oracle. Here is a reasonable starting point - it's not a trivial exercise to get it right. In particular, you probably want to look at DB_CACHE_SIZE.