Investigating transaction manager waits

Formatting a system dump using the keyword XM=1 provides a number of transaction manager summaries that are useful for identifying why tasks have failed to run.

A task may fail to run if the system is at MXT, or if the task is defined in a transaction class that is at its MAXACTIVE limit.

Maximum task condition waits

Tasks can fail to run if either of the following limits is reached:

If a task is waiting for entry into the MXT set of transactions, the resource type is MXT, and the resource name is XM_HELD. If a task is waiting for entry into the MAXACTIVE set of transactions for a TCLASS, the resource type is TCLASS, and the resource name is the name of the TCLASS that the task is waiting for.

If a task is shown to be waiting on resource type MXT, it is being held by the transaction manager because the CICS system is at the MXT limit. The task has not yet been attached to the dispatcher.

The limit that has been reached, MXT, is given explicitly as the resource name for the wait. If this type of wait occurs too often, consider changing the MXT limit for your CICS system.

Transaction summary

The transaction summary (Figure 13) lists all transactions (user and system) that currently exist. The transactions are listed in order of task number and the summary contains two lines per transaction.

The meanings of the column headings are as follows:

Tran id
The primary transaction id associated with the transaction
Tran num
The unique transaction number assigned to the transaction
Txn Addr
The address of the transaction control block
Txd Addr
The address of the transaction definition instance associated with the transaction
Start Code
The reason the transaction was attached, as follows:
C
A CICS internal attach
T
A terminal input attach
TT
A permanent transaction terminal attach
QD
A transient data trigger level attach
S
A START command without any data
SD
A START command with data
SZ
A front end programming interface (FEPI) attach
DF
Start code not yet known--to be set later.
Sys Tran
Indicator (Yes or No) of whether the transaction is attached as a system transaction. System transactions do not contribute towards MXT.
Status
An indicator of how far through attach the transaction has progressed and whether the transaction is abending or not. The first line may take the following values:
PRE
The transaction is in the early stages of attach.
TCLASS
The transaction is waiting to acquire membership of a tclass.
MXT
The transaction is waiting on MXT.
ACT
The transaction is active, that is, it has been DS attached.

Depending on the value in the first line, the second line of the status field may further qualify the transaction state. For each first line value, the meaning of the second line is as follows:

PRE
No data is displayed in the second line
TCLASS
The second line contains the name of the tclass that the transaction is waiting to join.
MXT or ACT
If applicable, the second line indicates if the transaction is flagged for deferred abend or a deferred message, or if the transaction is already abending, as follows:
DF(xxxx)
indicates that the transaction is scheduled for deferred abend, where xxxx is the abend code.
DM(yy)
indicates that the transaction is scheduled for a deferred message, and yy indicates the message type
AB(xxxx)
indicates that the transaction is already abending with abend code xxxx.
DS token
The token identifying the DS task (if any) assigned to the transaction.
Facility type
Type of the principal facility owned by the transaction.
Facility token
Transaction token for the principal facility owner.
AP token
The AP domain transaction token.

The first word of this token contains the address of the TCA (if any) associated with the transaction.

PG token
The program manager transaction token.
XS token
The security domain transaction token.
US token
The user domain transaction token.
RM token
The recovery manager transaction token.
SM token
The storage manager domain transaction token.
MN token
The monitoring domain transaction token.

Figure 13 shows a transaction summary.

Figure 13. Transaction summary
==XM: TRANSACTION SUMMARY
 
Tran Tran  TxnAddr Start Sys  Status   DS       Facility Facility AP       PG       XS       US       RM       SM
id   num   TxdAddr code  Tran          token    type     token    token    token    token    token    token    token
-----------------------------------------------------------------------------------------------------------------------
CSTP 00003 10106200 C    Yes  ACT      00120003 None     n/a      10164600 00000000 00000000 00000000 1016C000 10089020
           101793C0                                               01000000 1017E000 00000000 00000000 10164600 00000000
 
CSNE 00031 10106100 C    Yes  ACT      00000003 None     n/a      10164C00 00000000 00000000 00000000 1016C058 11542054
           10A34B40                                               01000000 1017E048 00000000 00000000 10164C00 00000000
 
IC06 10056 10E2B200 T    No   ACT      089601C7 Terminal 10E167A0 1124F600 00000000 00000000 10114023 1016C9A0 11543610
           10AC9300                                      00000000 00000000 1017E7E0 00000000 10E0F6A0 1124F600 00000000
 
IC12 10058 10E34C00 SD   No   ACT      050601AD None     n/a      001DE600 00000000 00000000 10114023 1016C9F8 11545114
           10AC93C0                                               00000000 1017E828 00000000 10E31400 001DE600 00000000
 
TA03 93738 10E0E000 T    No   ACT      088211E3 Terminal 10ED9000 0024B000 00000000 00000000 10114023 1016C738 115437B0
           10AD3D40                                      00000000 00000000 1017E090 00000000 10117D60 0024B000 00000000
 
TA03 93920 10AFF200 T    No   TCL      00000000 Terminal 11214BD0 00000000 00000000 00000000 10114023 00000000 00000000
           10AD3D40           DFHTCL03                   00000000 00000000 00000000 00000000 10117680 00000000 00000000
 
TA03 93960 10E2D200 T    No   TCL      00000000 Terminal 10E573F0 00000000 00000000 00000000 10114023 00000000 00000000
           10AD3D40           DFHTCL03                   00000000 00000000 00000000 00000000 10E0F6C0 00000000 00000000
 
TA03 93967 10AFEA00 T    No   TCL      00000000 Terminal 10ECCBD0 00000000 00000000 00000000 10114023 00000000 00000000
           10AD3D40           DFHTCL03                   00000000 00000000 00000000 00000000 10117540 00000000 00000000
 
TA03 94001 10E34800 T    No   ACT      00000000 Terminal 10E2C3F0 00000000 00000000 00000000 10114023 00000000 00000000
           10AD3D40           DF(AKCC)                   00000000 00000000 00000000 00000000 10E31120 00000000 00000000
 
TA02 95140 10E2D300 T    No   ACT      0386150D Terminal 10E2C5E8 00057000 00000000 00000000 10114023 1016C790 11544754
           10AD3C80                                      00000000 00000000 1017E510 00000000 10E0F320 00057000 00000000
 
TA02 95175 10E12C00 T    No   TCL      00000000 Terminal 10E937E0 00000000 00000000 00000000 10114023 00000000 00000000
           10AD3C80           DFHTCL02                   00000000 00000000 00000000 00000000 10E0F100 00000000 00000000
 
TA02 95187 10E0B000 T    No   TCL      00000000 Terminal 10EA95E8 00000000 00000000 00000000 10114023 00000000 00000000
           10AD3C80           DFHTCL02                   00000000 00000000 00000000 00000000 10117800 00000000 00000000
 
TA02 95205 10E2D600 T    No   MXT      00000000 Terminal 10E837E0 00000000 00000000 00000000 10114023 00000000 00000000
           10AD3C80           DF(AKCC)                   00000000 00000000 00000000 00000000 10E0F780 00000000 00000000
 
TA04 96637 10E33000 T    No   ACT      060408E7 Terminal 10E05BD0 00057600 00000000 00000000 10114023 1016C7E8 115457C8
           10AD3E00                                      00000000 00000000 1017E558 00000000 10E31040 00057600 00000000
 
TA04 96649 10E34000 T    No   TCL      00000000 Terminal 10AE89D8 00000000 00000000 00000000 10114023 00000000 00000000
           10AD3E00           DFHTCL04                   00000000 00000000 00000000 00000000 10E312C0 00000000 00000000
 
F121 99305 10E2D800 T    No   ACT      020C1439 Terminal 10EA93F0 00060000 00000000 00000000 10114023 1016C898 115423FC
           10AD3BC0           AB(AFCY)                   00000000 00000000 1017E708 00000000 10E0F920 00060000 00000000
 
TS12 99344 10AFED00 T    No   MXT      00000000 Terminal 10E499D8 00000000 00000000 00000000 10114023 00000000 00000000
           10AD6B40                                      00000000 00000000 00000000 00000000 101178C0 00000000 00000000

Notes for Figure 13

  1. Transactions 00003 and 00031 are system transactions.
  2. Transactions 93920, 93960, and 93967 are waiting because tclass DFHTCL03 is at its MAXACTIVE limit.
  3. Transaction 94001 is scheduled to abend AKCC because it was attached when tclass DFHTCL03 was at its PURGETHRESH limit.
  4. Transactions 95175 and 95187 are waiting because tclass DFHTCL02 is at its MAXACTIVE limit.
  5. Transaction 95205 was scheduled to abend AKCC because it was attached when tclass DFHTCL02 was at its PURGETHRESH limit. It was subsequently made to queue because CICS is at its MXT limit.
  6. Transaction 99305 is abnormally terminating with abend code AFCY.
  7. Transaction 99344 is queuing because the system is at its MXT limit.
  8. Transactions waiting in the transaction manager have no DS token, which is indicated by zeros in the summary.

MXT summary

The MXT summary indicates whether CICS is currently at MXT and shows the current number of queued and active transactions. To check the status of an individual transaction, consult the main transaction summary (Figure 13).

==XM: MXT SUMMARY
 
   Maximum user tasks (MXT):                 7
   System currently at MXT:                  Yes
   Current active user tasks:                7
   Current queued user tasks:                2
 * Peak active user tasks:                   7
 * Peak queued user tasks:                   2
 * Times at MXT limit:                       1
 
* NOTE: these values were reset at 18:00:00 (the last statistics interval collection)
 

Transaction class summary

The transaction class summary lists each transaction class that is currently installed. For each class, the current number of active and queued transactions is shown. A transaction class is at its MAXACTIVE limit if its ‘current active’ total is greater than or equal to its ‘max active’ setting. If a transaction class is at its MAXACTIVE limit, a number of transactions may be queueing in that transaction class. The transaction id and number of each queued transaction is listed with its transaction class (for example, transaction classes DFHCTL01, DFHCTL02, and DFHCTL03 in Figure 14).

Figure 14. Transaction class summary
==XM: TCLASS SUMMARY
 
 Tclass       Max     Purge    Current   Current     Total    Queuing  Queuing      Queuing
  Name      Active  Threshld    Active    Queued  Attaches    TranNum  Transid     Start Time
--------  --------  --------  --------  --------  --------    -------   ----     ------------
DFHTCL01         1         0         0         0         0
DFHTCL02         1         3         1         2         7    95175     TA02     18:00:19.677
                                                              95187     TA02     18:00:24.624
DFHTCL03         1         4         1         3        29    93920     TA03     17:55:40.584
                                                              93960     TA03     17:55:42.230
                                                              93967     TA03     17:55:52.253
DFHTCL04         1         0         1         1        23    96649     TA04     18:06:04.348
DFHTCL05         1         0         0         0         0
DFHTCL06         1         0         0         0         0
DFHTCL07         1         0         0         0         0
DFHTCL08         1         0         0         0         0
DFHTCL09         1         0         0         0         0
DFHTCL10         1         0         0         0         0
 
*** Note that the 'Total Attaches' figures were reset at 18:00:00 (the last statistics interval collection)

A user task is waiting on resource type FOREVER

If you have found that a user task is waiting on a resource type of FOREVER, and resource name DFHXMTA, transaction manager has detected a severe error during task initialization or task termination. Transaction manager has suspended the task.

The suspended task is never resumed, and holds its MXT slot until CICS is terminated. You must cancel CICS to remove this task as you will be unable to quiesce the system. You cannot purge or forcepurge the task.

This wait is always preceded by one of the following messages: DFHXM0303, DFHXM0304, DFHXM0305, DFHXM0306, DFHXM0307, DFHXM0308, DFHXM0309, DFHXM0310. Transaction manager also takes a dump and message DFHME0116 is produced and contains the symptom string.

Resource type TRANDEF

The suspended transaction has attempted to update the transaction definition identified by the transaction ID but found it already locked by another transaction.

Related tasks
Formatting system dumps
Setting the maximum task specification (MXT)
Using transaction classes (MAXACTIVE) to control transactions
Specifying a transaction class purge threshold
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