SYSIBM is an IBM-supplied which was created during the installation of, or upgrade to, OS/400 V5R2. Though SYSIBM is does not follow the Q library naming conventions, it is considered a system supplied library, like QSYS, and it and its contents should not be deleted or altered.
System library SYSIBM added
"SYSIBM has been added as a new system library in V5R2. The SYSIBM library, reserved for use by DB2 UDB for iSeries, is created during the installation process. If a library named SYSIBM already exists, the library attributes (including ownership, public authority and text description) are changed, but no objects are deleted from the library. Like other system libraries, the SYSIBM library cannot be deleted, renamed, or cleared. The SYSIBM library will be included in the list of libraries when special value *ALLUSR is specified as the library name; for example, when LIB(*ALLUSR) is specified on the Save Library (SAVLIB) command."
- PDF of iSeries Memorandum to Users Version 5 Release 2 (June 2006 Update)