Friday, November 16, 2012

Where to find information about granted privileges in DB2

Yesterday, I reveived a question about where to find specific metadata in DB2. The customer wanted to find out which privileges had been granted within a database and they were aware that db2look can produce this list. But where does this information come from?

Let's start with a glimpse at db2look. It is the "DB2 statistics and DDL extraction tool" and can be used to produce the DDL statements for the objects inside a database. There are also options specific to handling authorizations, i.e., the privileges (see the -x, -xdep, -xd, and -xddep options). All the statements that db2look produces are based on special data stored in the database, the so-called metadata. Those tables that hold the metadata are called System Catalog in DB2 and Data Dictionary in Oracle. The system catalog than can be queried using regular SELECT statements because the information is provided in tables (users can stay within the data mode, the relation model).

DB2 offers the metadata in two different sets of views. The views in the SYSCAT schema basically have all the metadata. The views in the SYSSTAT schema have a subset of the data and have (some) updatable columns, so that object statistics can be changed (for good or for worse...). The views are built on top of the internal catalog tables which are managed in the SYSIBM schema. It is advised to only use the SYSCAT and SYSSTAT views because structure of the internal tables can change without warning whereas the external catalog views are kept intact.

Now, where can the information about granted privileges be found? The DB2 Information Center has a so-called "Road map to catalog views" which is a listing of all the offered metadata found in the SYSCAT and SYSSTAT views. All the views that end in *AUTH carry authorization information, i.e., data about privileges. To give some examples, in SYSCAT.INDEXAUTH you can find out who has CONTROL privilege on an index, SYSCAT.ROLEAUTH is useful to see who has ADMIN authority for granting a specific role, and finally, as a complex example, SYSCAT.TABLEAUTH manages all the table privileges like insert, update, delete, select, alter, control, and even more privileges.

Administration tools for DB2 access that information, procedures and scripts can select data from these views, and of course applications and users. Which of these views are made available for the PUBLIC is up to the administrators. Remember, it's an honor, not a privilege...

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