DB2 writes transactions to the log buffer. This buffer is flushed periodically. The flush happens when either the buffer pool is cleaned, or when it is full. DB2 has the ability to read pages from disk into the buffer pool before the application needs them. This is called "prefetching". It is highly recommended that the RUNSTATS program be run periodically to ensure optimal performance.
Frequently you will receive error messages when using the DB2 database. For example you might get the SQL0911N if there is a deadlock that is detected and resolved by DB2. The "SQL" in the SQL0911N error number means that this is an error that comes from the Database Manager. This is the most common error you will encounter as a database developer.
It the event that you suspect that an error is a DB2 bug, technical support may request that you run the db2support utility. It collects all kinds of information and stores it in a file named "db2support.zip". Guess what type of file this is?
The system catalog is contained in the SYSIBM schema. There are read only views for SYSIBM tables in the SYSCAT schema. For example, SYSCAT.TABLES is a view for the underlying SYSIBM.SYSTABLES table.
There is an entity called the Communications Database (CDB) in DB2. It is currently a set of system table with connection information. They are stored in the host database. The CDB used to be a separate database in prior versions of DB2. However it is not part of the catalog.
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