Finding out how much space a library uses

The library total:

SELECT OBJECT_COUNT, LIBRARY_SIZE / 1024 / 1024 AS MB, LIBRARY_SIZE_COMPLETE
  FROM TABLE(QSYS2.LIBRARY_INFO('PRODLIB'))

LIBRARY_SIZE is in bytes and includes the objects and the library itself; above a billion bytes it is rounded. If LIBRARY_SIZE_COMPLETE is NO, some objects were left out because they were locked or you have no authority to them. IBM warns that on a library with many objects the calculation can take time.

But the total is of little use: what matters is who is taking the space.

SELECT OBJNAME, OBJTYPE,
       OBJSIZE / 1024 / 1024 AS MB,
       LAST_USED_TIMESTAMP
  FROM TABLE(QSYS2.OBJECT_STATISTICS('PRODLIB', '*ALL'))
 ORDER BY OBJSIZE DESC
 FETCH FIRST 20 ROWS ONLY

The largest libraries on the system, when you do not know where to start:

SELECT L.OBJNAME AS LIBRARY, I.LIBRARY_SIZE / 1024 / 1024 AS MB
  FROM TABLE(QSYS2.OBJECT_STATISTICS('QSYS', '*LIB')) L,
       TABLE(QSYS2.LIBRARY_INFO(L.OBJNAME)) I
 ORDER BY I.LIBRARY_SIZE DESC
 FETCH FIRST 20 ROWS ONLY

It computes the size of every library on the system, so it is slow: run it when you have the time. Sorting libraries by the OBJSIZE of OBJECT_STATISTICS does not help, because that is the size of the library object, not of its contents.

Example: the library that grows and nobody knows why

Knowing that PRODLIB takes 40 GB says nothing. Knowing it took 28 six months ago, and which objects took the 12 GB difference, says everything.

One snapshot a month, in a table created from the query itself:

CREATE TABLE MYLIB/SIZEHIST AS (
  SELECT CURRENT DATE AS TAKEN_AT, OBJNAME, OBJTYPE, OBJSIZE
    FROM TABLE(QSYS2.OBJECT_STATISTICS('PRODLIB', '*ALL'))
) WITH NO DATA

Then the comparison between two snapshots, which is the query that earns its keep:

SELECT o.OBJNAME, o.OBJTYPE,
       n.OBJSIZE - o.OBJSIZE AS GROWTH
  FROM MYLIB/SIZEHIST o
  JOIN MYLIB/SIZEHIST n
    ON n.OBJNAME = o.OBJNAME AND n.OBJTYPE = o.OBJTYPE
 WHERE o.TAKEN_AT = '2026-02-01'
   AND n.TAKEN_AT = '2026-08-01'
 ORDER BY GROWTH DESC
 FETCH FIRST 20 ROWS ONLY

The answer may be, for instance, an application log file nobody empties, or a work table that was meant to be temporary.

Releases. OBJECT_STATISTICS and LIBRARY_INFO are in IBM's 7.5 documentation. If either answers SQL0204 on an older release, a library's total also comes from RTVLIBD, of which LIBRARY_INFO is the SQL equivalent.

Sources

• IBM: LIBRARY_INFO table function
• IBM: OBJECT_STATISTICS table function