Introduction
There are a few new features for sharding. The key ones are listed below with a brief sdescription.
Multi-Shard Query Coordinators on Standby Databases
Prior to 19c, the multi-shard query coordinator could only exist ony the primary shard catalog database. From 19c onward, this changes and the multi-shard query coordinator can exist on the active standby database.
Unique Sequence Numbers Across Shards
Prior to 19c, unique sequences numbers across shards need to be created and managed by the user/application. From 19c onward, globally unique sequence numbers can be generated across shards. The following command can be used to create them
- SQL> CREATE or ALTER SEQUENCE <sequence name> ……. SHARD or NOSHARD
Multiple PDB Shards in the Same CDB
You can now have >1 PDBs in a Container Database for shards or shard catalogs
Multiple Table Families
Multiple table families can be sharded across a database with different sharding keys.
Note - . This feature applies to system-managed sharded databases.
Propagation of Parameter Settings Across Shards
Prior to 19c, you had to configure the parameters for each sharded DB separately. From now on, you can add an extra shard=all parameter to the alter system command. See below
- SQL> alter system <parameter> shard=all;
