The CCILGR/Assured Delivery component of CAICCI is required for sites that run CA ACF2/CPF. CCILGR is built upon the fundamental mechanisms of VSAM file access. This component is a store and forward application. As such, data is received, written, and stored in the VSAM database and then read before being sent out. When the data is sent, it remains in the VSAM file until the local CCILGR receives confirmation from the data recipient that the data arrived intact. When the confirmation is received, CCILGR deletes the record from the database. CA ACF2/CPF command propagation requires its own response to prevent duplicate data. Due to the constant reads, writes, and deletes, the CCILGR database is dynamic.
The product uses keyed sequential file access to VSAM to ensure that data is delivered securely, with integrity, and in the proper sequence. The keys are linked to the time the record was written, so every key is unique. The keys cannot be duplicated or reused. Because the access is keyed and sequential, inbound records are written to the end of the file. These records must be read again before being sent to their destination. Additionally, every read must begin at the top of the file and must traverse all existing records until the one to be processed is encountered. Over time, the database fragments with CA/CI splits. If the amount of data being delivered within a sysplex of many systems is large, performance could be affected.
One of the major reasons to reorganize the CCILGR VSAM file is when Control Areas become unusable. Messages remain in the VSAM file for a long time under the following circumstances:
This situation eventually causes Control Areas to fill up. When a control area becomes full, it is associated with a specific date and time range. VSAM does not reuse that control area even after all of the records in it have been delivered to the receiver and deleted from the file. The only way to reclaim those Control Areas is to reorganize the file.
With z/OS 1.12, a new VSAM option became available named CA Reclaim. With this option enabled, when a Control Area becomes empty, it is not associated with a specific date and time range. This area can then be used to store new records. This setup eliminates the need for frequent reorganizations. Even with this option enabled, we recommend that you reorganize the CCILGR VSAM (weekly or monthly).
The CA Reclaim option is disabled by default on a system level. This option is enabled by default for all KSDSs, without having to redefine the data set. To turn on CA Reclaim at the system level, update member IGDSMSxx in SYS1.PARMLIB to contain the new parameter “CA_RECLAIM(DATACLAS)”. This parameter lets VSAM reclaim newly emptied Control Areas in all VSAM files. For more information, see the IBM z/OS MVS Initialization and Tuning Reference.
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