Follow the tips in the following table to ensure that your TDP cells are tuned for optimum performance.
| Question | Answer | |
|---|---|---|
| How do I know whether to add regular cells or PC cells when I experience a cell shortage? | If a normal cell pool is
exhausted, a TDP0021 message is issued. If an XMS cell pool is
exhausted, either a TDP0201 or TDP0202 message is issued. The response to a DISPLAY CELLS command will also indicate cell exhaustion. For a normal cell pool, a TDP0528 message indicates the number of exhaustions. For an XMS cell pool, the TDP1520 and the TDP1521 messages indicate exhaustions. |
|
| When can I use the ADD CELLS command? | The ADD CELLS command
can be used in the following circumstances:
Do not use ADD CELLS as a TDPPARM dataset parameter if you want to add 12,272 byte cells; instead, use INITIAL IOBUFS. |
|
| When can I subtract cells? | Subtracting cells is not allowed. Whenever TDP starts, cell allocations return to the TDP defaults unless the TDPPARM dataset parameters have one of the following commands:
|
|
| How do I change the number of Input/Output buffers? | Use the INITIAL IOBUFS
command to specify the number of Input/Output data buffers. IOBUFS are not used for CPs requiring
the CCU operand on the START command, and all NPs. These CPs and NPs
automatically manage their I/O buffers.
|
|
| What is the default number of cells used for Input/Output? | 6 per CP. This is true both for 480 byte and 12,272 byte cells. More highly stressed NPs or CPs should be allocated more cells. To do this, use either ADD CELLS (while TDP is running) or INITIAL IOBUFS (in the TDPPARM dataset). IOBUF cells (12,292 byte cells) are not
used for CPs requiring the CCU operand on the START command. Exclude
these CPs when considering the default cell size.
|
|
| What are the most important cell sizes and what are they used for? | There are four common
cell sizes. The 480 and 12,272 byte sizes (also known together as
I/O buffers or IOBUFS) are both needed for I/O. Common uses are explained in the following table. |
|
| Cell size (bytes) | Usage | |
| 240 | 1 cell is required per session. 1 cell is required per interface processor. |
|
| 992 | Request and response buffers | |
| 480 | Move requests and responses across the channel between the client and the database. | |
| 12,272 | For CPs started without the CCU operand on the START command, move requests and responses across the channel between the client and the database. | |