Restrictions on using calls for MSDBs

To retrieve segments from an MSDB, you can issue Get calls just as you do to retrieve segments from other IMS databases. Because MSDBs contain only root segments, you only use GU and GN calls (and GHU and GHN calls when you plan to update a segment). If the segment name field in the SSA contains *MYLTERM, the GU, GHU, and FLD calls return the LTERM-owned segment, and the remainder of the SSA is ignored.

When you are processing MSDBs, you should consider the following differences between calls to MSDBs and to other IMS databases:

  • You can use only one SSA in a call to an MSDB.
  • MSDB calls cannot use command codes.
  • MSDB calls cannot use multiple qualification statements (Boolean operators).
  • The maximum length for an MSDB segment key is 240 bytes (not 255 bytes, as in other IMS databases).
  • If the SSA names an arithmetic field (types P, H, or F) as specified in the database description (DBD), the database search is performed using arithmetic comparisons (rather than the logical comparisons that are used for DL/I calls).
  • If a hexadecimal field is specified, each byte in the database field is represented in the SSA by its two-character hexadecimal representation. This representation makes the search argument twice as long as the database field.

    Characters in hexadecimal-type SSA qualification statements are tested for validity before translation to the database format. Only numerals 0 through 9 and letters A through F are accepted.

  • Terminal-related and non-terminal-related LTERM-keyed MSDBs are not supported for ETO or LU 6.2 terminals. Attempted access results in no data being retrieved and an AM status code. See IMS Version 15.4 Communications and Connections for more information on ETO and LU 6.2.
  • MSDBs cannot be shared among IMS subsystems in a sysplex group. When using the Fast Path Expedited Message Handler (EMH), terminal related and non-terminal related with terminal key MSDBs can only be accessed by static terminals. These static terminals run transactions with Sysplex Processing Code (SPC) of Locals Only as specified in DBFHAGU0 (Input Edit Router exit routine).

The restrictions above do not apply to CICS® users.