db_cache_size and its association with db_block_size

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db_clock_size is the parameter that specifies the size of a block in an oracle database. In an Oracle database the basic unit of storage is blocks. As this stores data it is also called the data block

db_cache_size is the size of database buffer cache. This is the cache size associated with standard database block size

Oracle offers an option of non-standard block sizes in ranges of 2,8,16,32 and is an useful option with transportable tablespaces. To cater the non-standard block size requirement the db_cache_size can be set using db_nk_cache_size parameter

Say the non-standard block size is 16KB ,now the db_nk_cache_size would be db_16k_cache_size.

Temporary tablespace is always created with default block size

The value of db_nk_cache_size can be altered dynamically using alter system command

In an oracle environment with standard block size the default value of db_nk_cache_size would be 0MB

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Mongodb sharding architecture and overview

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Mongodb offers plenty of features and options to support big data, high volume throughput application, data availability etc. Sharding is an interesting feature of MongoDB that supports this high availability, scaling of big data.
What is sharding?
Before tlking about sharding lets talk about two types of scalability
Vertical scalability – Adding more RAM, CPU, Disk Space to cater growing needs
Horizontal scalability – Use more than one physical machine, distribute data across machines, club them together as single logical databse
MongoDB offers horizontal scalability utilizing sharding feature.
What components do make a shard?
A shard is a machine in real world. Plenty of physical machines are clustered together as a single sharded cluster.
1) Query router – This is the mongos instance which interacts with client and routes query to appropriate shards
2) Config servers – In a typical production environment there are 3 config servers. They store metadata on cluster configuration
3) Shards – The machines storing logically partitioned information
What is the key behind partitioning in shard?
Shard keys help with partitioning in shards

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