RAPOOL

The RAPOOL system initialization parameter specifies the number of concurrent receive-any requests that CICS® is to process from the z/OS® Communications Server for SNA.

RAPOOL={50|value1|(value1,value2,FORCE)}
value1 is the number of fixed request parameter lists (RPLs), receive any control elements (RACEs), and receive any input areas (RAIAs) that are to be generated whether or not CICS uses the high performance option (HPO). value1, in the range 1 through 999, is also the number that are active in a non-HPO system; value2, in the range 0 through 999, is the number that are active in an HPO system. The default for value1 in the DFHSIT macro is 50. The default for value2 is calculated from value1 as follows:
  • If value1 = 1, value2 = 1
  • If value1 ≤ 5, value2 = (value1 minus 1)
  • If value1 ≥ 6 and ≤ 50, value2 = 5
  • If value1 > 50, value2 is 10 per cent of value1
Note: Code value1 equal to or greater than value2; if you code value1 less than value2, CICS forces value2 equal to value1.
If you omit the RAPOOL parameter altogether, RAPOOL=(50,5) is assumed. CICS maintains n z/OS Communications Server RECEIVE ANYs, where n is either the RAPOOL number active value, or the MXT value minus the number of active tasks, whichever is the smaller. For example, in a non-HPO system:
  • If RAPOOL=2, MXT=50, active tasks = 45, then RECEIVE ANY = 2
  • If RAPOOL=10, MXT=50, active tasks = 45, then RECEIVE ANY = 5
  • If RAPOOL=10, MXT=50, active tasks = 35, then RECEIVE ANY = 10
In an HPO system:
  • If RAPOOL=(20,10), MXT=50, active tasks = 45, then RECEIVE ANY = 5

FORCE tells CICS to free up Receive_Any_RPLs if they are stalled. CICS decides that the Receive_Any_RPLs are stalled if all the RA RPLs have been posted but the TCTTE for each one is waiting for a response from a z/OS Communications Server terminal or session for 10 dispatches of the TCP (CSTP) task.

This typically happens only if a protocol error has occurred, and sessions are waiting for a response; for example, to a BID SHUTD request from CICS.

Each session is unbound, the Receive_Any data is lost and the RA RPL is reissued thus allowing z/OS Communications Server activity to continue: Message DFHZC4949 is issued for each session affected.

Consider increasing the size of the RAPOOL before resorting to the use of FORCE.

If FORCE is not specified and a Receive_Any stall occurs, DFHZC2118 is written to the console for each session affected.

If FORCE is specified in the SIT, and RAPOOL is supplied as an override, you must again specify FORCE as otherwise it defaults to FORCE not specified.

The number of RECEIVE ANYs needed depends on the expected activity of the system, the average transaction lifetime, and the MAXTASK value specified. For information about coding this parameter, see the Setting the size of the receive-any pool.