CCAMDMP data sets
Note: Allocating CCAMDMP data sets to hold multiple asynchronous dumps of the Model 204 address space has been deprecated in favor of using the SNAPCTL parameter.
Overview
As an alternative to taking a high-speed, unformatted dump of the Model 204 address space, z/OS users can use an extended version of the SYSMDUMP facility to take up to ten unformatted dumps of the Model 204 address space. This is described in the following sections.
Allocating SYSMDUMP data sets
To allocate multiple SYSMDUMP data sets, insert one to ten DD statements with ddnames CCAMDMP0, CCAMDMP1, and so on. The following rules apply to the use of CCAMDMP data sets:
- Only empty CCAMDMP (0 - 9) data sets are selected for SYSMDUMP processing. At any time during the run, each data set contains at most one dump. This prevents SYSMDUMP processing from destroying or overwriting previous dump data sets.
- Use of tape data sets is not supported. The CCAMDMP data sets must be preallocated on disk devices.
- If the CCAMDMP allocations are
DISP=SHR, then you can clear, copy, or analyze any of the data sets without bringing down the Model 204 Online. - If an error occurs while allocating a CCAMDMP data set, allocation is not attempted again for the remainder of the run.
- If all CCAMDMP data sets are full, then SYSMDUMP processing terminates and either SYSUDUMP or SYSABEND is used for further ABDUMP processing, if either of these is specified in the JCL. Use of SYSUDUMP or SYSABEND statements in case of overflow is not recommended, however. These auxiliary data sets are more likely to fill up spool space than to provide important diagnostic information.
- CCAMDMP and SYSMDUMP DD statements are incompatible. If a SYSMDUMP statement is present, then the CCAMDMP statements are ignored, and multiple dump data sets cannot be created.
- Note that CCAMDMP data sets must be allocated on single extents.
Number of CCAMDMP data sets
The optimum number of CCAMDMP data sets is normally equal to the value of the SNAPLIM parameter.
CCAMDMP data set DCB characteristics
DCB characteristics of CCAMDMP data sets must be the same as those recommended for the standard z/OS SYSMDUMP facility, shown in the following table:
| System | Organization | Record format | LRECL | BLKSIZE |
|---|---|---|---|---|
| z/OS | PS | FB or F | 4160 | 4160 |
Space allocation
To estimate the space required for each CCAMDMP data set, add four megabytes to the size of the Model 204 address space. For example, a 20M address space needs 24M, or about 40 cylinders on a 3380 disk device.
Size of Model 204 address space
The address space actually used in a Model 204 run can depend on several factors in addition to the REGION parameter. For more information on this topic, refer to the IBM z/OS documentation.
Coordinating use of CCAMDMP and CCASNAP data sets
You can allocate both CCAMDMP and CCASNAP data sets in a Model 204 run. An advisable setting for CCASNAP is SNAPPDL. The CCASNAP data set is then useful for quick diagnosis, while the CCAMDMP data sets provide more complete information.
Processing CCAMDMP data sets
You can process CCAMDMP data sets allocated in share mode using standard utilities such as IEBGENER. To archive and clear a dump data set, for example, copy it to tape, then copy a null file to the disk data set.