Locating Fast Path control blocks and tables
Many of the Fast Path control blocks are extensions of IMS full-function control blocks. The names of these Fast Path control blocks are the same as in full-function.
The acronyms for these Fast Path control blocks start
with E.
- SCD
- System Contents Directory (full-function IMS)
- ESCD
- Extended System Contents Directory (Fast Path)
To view the layout of the Fast Path control blocks for your system, assemble DFSADSCT from IMS.ADFSSMPL and use XREF(FULL).
The following table shows the Fast Path control blocks and work areas that appear as a load list in an IMS dump. This information is relevant when you are working on an abend U1011 in module DBFINI20. Message DFS2703A generally accompanies the abend. Abend U1011 results from either a GEN problem or a storage fragmentation problem.
| Load list name | Fast Path block/work area | Appearance in dump |
|---|---|---|
| DFSEPnnn | Fast Path EPSTs |
IMS STM task |
| DBFCONT1 | ECNTs/MSDBs | IMS STM task |
| DBFCONT3 | DMHRs/buffers | IMS STM task |
| DBFCONT4 | DEDB blocks | IMS STM task |
| DBFCONT5 | OTHREADs | IMS STM task |
| DBFCONT6 | BALGs | IMS STM task |
| DBFCONT7 | Miscellaneous buffers | IMS STM task |
| AREALIST | AREA list | IMS STM task |
At Fast Path initialization, modules DBFINI21, DBFINI23, DBFINI24, DBFINI25, DBFINI26, and DBFINI27 calculate the amount of contiguous ECSA storage that is needed to load the buffers, buffer headers, MSDBs, and other related control blocks into separate work areas named DBFCONTx.
If module DBFINI2x cannot obtain a large enough contiguous block of storage, abend U1011 is issued, along with an error message. When this abend occurs, you can restart IMS, or you can stop other jobs that might prevent module DBFINI2x from obtaining the necessary storage.
The following table describes the control block structures that are defined during IMS startup. This table can help you determine which control blocks are needed in your Fast Path environment.
| Control block/table | With MSDB/DEDB | Without DEDB | Without MSDB | Without MSDB/DEDB |
|---|---|---|---|---|
| ECNT DBFCONT1 | X | X | X | X |
| BHDR DBFCONT1 | X | X | ||
| MSDB DBFCONT1 | X | X | ||
| DMHR DBFCONT3 | X | X | X | |
| BUFF DBFCONT3 | X | X | X | |
| DEDB blocks (DMCBs, DMACs, MRMBs, segment names, and field names) DBFCONT4 | X | X | ||
| OTHR DBFCONT5 | X | X | ||
| BALG DBFCONT6 | X | X | X | X |
| LBUF DBFCONT7 | X | X | X | X |
| FPAL AREALIST | X | X |