Is SYSIBM a DB2 internal user or is it just a schema name in DB2? In the SYSCAT.TABLESPACES catalog view, the definer of the default tablespaces in DB2 is mentioned as SYSIBM. For user created Tablespaces, the definer represents the name/ID of the user who created the tablespace.

Can SYSIBM be regarded as an internal user of DB2?

To the best om my knowledge SYSIBM is not a user
First of all it doesn't appear on the OS as a user and
its not used for running anything.

It's simply a schema containing system tables and
related content - having the extra check that its
impossible to create new tables in.

SY

It is a schema for catalogue tables.