Optimizing read expression generation

Read expressions map to a given object and record its read access characteristics for any given user, group, role, and session parameter (for example, session projects). Teamcenter automatically maintains read expressions by regenerating and updating them whenever objects are modified. Use the am_read_expression_manager utility to generate these expressions. By default, this utility is active as a service. Depending on which mode you select, this utility: Updates stale read expressions. Creates new read expressions. Manages changes based on rule tree updates. Deletes superfluous data. Objects without read expressions, which the system loads as part of any BOM expand or search, are marked to receive read expressions generated by the am_read_expression_manager service when it performs an update. Read expression generation can be optimized using the following techniques: Read expression daemon execution parameters Pre-instrumentation of read expressions for specific sets of objects Rule tree updates Read expression daemon execution parameters Use the daemon mode of the am_read_expression_manager utility to update stale read expressions for business objects. The following parameters determine how and when the read expression daemon process runs: Sleep time Specifies the time, in seconds, during which the process remains dormant. The default is 10. Spawn intervals Specifies the number of repeated executions of the daemon before a new process is spawned. The default is 500; however, this depends on the total number of objects processed. You can specify these parameters either: In the command line if the daemon process is involved within a shell. Or, as a preference if the process runs as a service. The service checks these values either when first executing or when re-spawning. Preference Name Type Function RE_MGR_sleep_time Integer Sleep time, in seconds, between executions. The default is 10. RE_MGR_exec_count Integer Execution count until a new daemon is spawned. The default is 500. RE_MGR_concurrency_objs_threshold Integer Threshold value of stale read expressions. The default is 1,000,000. To limit the read expression daemon process in the event of performance problems pertaining to system response times, Siemens Digital Industries Software suggests you set the daemon sleep time equal to the average daemon processing time per interval. You can view this time in the daemon execution console output. This suppresses the daemon speed to about 50 percent of maximum speed, thereby improving your system performance. Pre-instrumentation of read expressions for specific sets of objects The am_read_expression_manager utility allows identification of business objects for which read expressions can be force generated. To do this, query execution and/or UID list input is possible. This inserts new stale read expression placeholders into the associated tables. However, these then have to be computed according to the rule tree and the objects involved, which can be time consuming. You should perform this pre-instrumentation immediately after an installation or upgrade, as not many objects have received read expressions. Otherwise, many business-relevant objects will have automatically received read expressions and the benefit of this pre-instrumentation is diminished. Siemens Digital Industries Software recommends the following best practice if you require this upfront computation of read expressions: For those sets of objects that have been identified to be relevant for business needs and should have read expressions as early as possible, perform a dry run of the associated query to obtain the total number of affected objects. Determine how many objects per hour can be processed by the daemon in your system. You can calculate this using the daemon command shell output for individual processing intervals and computing an average. Using these two numbers, establish a timeline for computation of such read expressions. You should perform this during a quiet time in your system, for example, at night or during a weekend. Note that multiple pre-instrumentation daemon processes must run consecutively; multiple daemon processes cannot run in parallel. Rule tree updates Rule tree updates change the security profile of objects and potentially invalidate large numbers of read expressions of business objects. When such rule tree updates occur, the associated read expressions are examined and marked as stale if impact is perceived. Every attempt is made to limit the number of such invalidations; however, at times it may be necessary to invalidate large numbers of read expressions and potentially the entire read expression table. If your rule tree requires updating a substantial number of objects, Siemens Digital Industries Software recommends you perform the rule tree update during the start of a quiet time to allow the read expression daemon adequate time to process updates before users are online.