一、参数应用场景
PURGEOLDEXTRACTS 常用于OGG清理Trail文件所需，如果不配置这个参数，或者参数失效，可能导致目录空间满！
那么这个参数如何配置？ 有哪些特征
二、参数说明
使用这个参数可以清理OGG Trail日志,在MGR参数配置 PURGEOLDEXTRACTS for Manager Valid For Manager Description Use the PURGEOLDEXTRACTS parameter in a Manager parameter file to purge trail files when Oracle GoldenGate has finished processing them.
Without using PURGEOLDEXTRACTS, no purging is performed, and trail files can consume significant disk space. Using PURGEOLDEXTRACTS as a Manager parameter is recommended rather than using the Extract or Replicat version of PURGEOLDEXTRACTS.
As a Manager parameter, PURGEOLDEXTRACTS allows you to manage trail files in a centralized fashion and take into account multiple processes. How to Use PURGEOLDEXTRACTS for Manager 第一个规则是否检查Trail文件的检查点信息; 第一个参数,USECHECKPOINTS默认值,这个参数的意思是Trail文件对应的所有进程的检查点都确认完成后,OGG MGR进程才能将其进行删除！ To control the purging, follow these rules: USECHECKPOINTS triggers a purge when all processes are finished with a file as indicated by their checkpoints. Basing the purges on
checkpoints ensures that Manager does not delete any data until all processes are finished with it. This is essential in a production
environment to ensure data integrity. USECHECKPOINTS considers the checkpoints of both Extract and Replicat before purging.
Because USECHECKPOINTS is the default, it need not be specified in the PURGEOLDEXTRACTS statement. Manager obeys USECHECKPOINTS unless
there is an explicit NOUSECHECKPOINTS entry. 另外一个规则就是MINKEEP,规定保留时间 Use the MINKEEP rules to set a minimum amount of time to keep data: 保留的小时|天数 Use MINKEEPHOURS or MINKEEPDAYS to keep data for n hours or days. 保留的文件数量,默认是1 Use MINKEEPFILES to keep at least n trail files including the active file. The default number of files to keep is 1. 建议仅使用其中一个选项,如果使用多个则！ 小时与天参数都在，则选择一个！具体选择谁暂时没说， 小时|天与文件数量都在，则文件数量参数被忽略！ Use only one of the MINKEEP options. If more than one is used, Oracle GoldenGate selects one of them based on the following: If both MINKEEPHOURS and MINKEEPDAYS are specified, only the last one is accepted, and the other is ignored. If either MINKEEPHOURS or MINKEEPDAYS is used with MINKEEPFILES, then MINKEEPHOURS or MINKEEPDAYS is accepted, and MINKEEPFILES is ignored. 检查点+没有指定时间，则Trail文件确保被完全处理就进行删除,除非这个触发保留最少一个文件的规则 USECHECKPOINTS without MINKEEP rules: If checkpoints indicate that a file has been processed completely, it will be purged unless doing
so would violate the default rule to keep at least one file. 检查点+指定时间,则Trail文件需要确保文件被处理以及符合保留时间的策略！ USECHECKPOINTS with MINKEEP rules: If checkpoints indicate that a file has been processed completely, it will be purged unless doing so
would violate the MINKEEP rules. 不检查检查点+没有指定时间,则直接删除,除非这个触发保留最少一个文件的规则 NOUSECHECKPOINTS without MINKEEP rules: The checkpoints are not considered, and the file will be purged unless doing so would violate the
default rule to keep at least one file. 不检查检查点+指定时间,则只要不违反保留时间,则进行删除！ NOUSECHECKPOINTS with MINKEEP rules: A file will be purged unless doing so would violate the MINKEEP rules. 如果是NFS存储,需要考虑NFS远程服务器与本地操作系统的时间差,NFS时间创建的Trail文件与本地系统时间需要进行考虑,配置保留时间需要考虑时区！ When trails are stored on NFS, there is a difference in system time between the NFS drive and the local system where Manager is running.
The trail is created with the NFS time, but the timestamps of the records in the trail are compared with the local system time to determine
whether to purge them or not. Take into account any time differences when you create your MINKEEP rules. trail 清楚的Trail文件名称 The trail to purge. Use a relative or fully qualified name. USECHECKPOINTS 在所有的抽取、复制进程使用检查点确认数据处理完成后,才能被删除 Allows purging according to any MINKEEP rules after all Extract and Replicat processes are done with the data as indicated by checkpoints.
When using USECHECKPOINTS, you can use the USERID or USERIDALIAS parameters in the Manager parameter file,
so that Manager can query the Replicat checkpoint table to get checkpoint information though it is not required. NOUSECHECKPOINTS 不考虑检查点信息！ Allows purging without considering checkpoints, based either on the default rule to keep a minimum of one file (if no MINKEEP rule is used)
or the number of files specified with a MINKEEP rule. MINKEEP_rule 保留规则 Can be one of the following to set rules for the minimum amount of time to keep an inactive file. MINKEEPHOURS n 小时 Keeps an inactive file for at least the specified number of hours. The minimum is 1 and the maximum is 1000. MINKEEPDAYS n 天 Keeps an inactive file for at least the specified number of days. The minimum is 1 and the maximum is 365. MINKEEPFILES n 文件数量 Keeps at least n trail files, including the active file. The minimum is 1 and the maximum is 100. The default is 1. frequency 清理的频率,默认为10分钟一次,这个参数收到CHECKMINUTES的影响, 在这个10分钟的间隔内,受到参数PURGEOLDEXTRACTS frequency 选型的影响！ Sets the frequency with which to purge inactive trail files. The default time for Manager to evaluate potential maintenance
tasks is 10 minutes, as specified with the CHECKMINUTES parameter. At that interval, Manager evaluates the PURGEOLDEXTRACTS
frequency and conducts the purge after the specified frequency. 清理调用的频率可以是以下的几种可能之一 frequency can be one of the following: FREQUENCYMINUTES n 分钟设置频率,默认清除频率60分钟,范围1-360 Sets the frequency in minutes. The default purge frequency is 60 minutes. The minimum is 1 and the maximum is 360. FREQUENCYHOURS n 小时设置频率,1-24 Sets the frequency in hours. The minimum is 1 and the maximum is 24. CHECKMINUTES MGR管理进程间隔一定分钟的周期,进行活动检查、包括清理历史文件调用等等,默认10分钟一次！ Use the CHECKMINUTES parameter to control how often Manager performs maintenance activities. Decreasing this parameter
can significantly affect performance if trail files roll over frequently. Other events, such as processes ending abnormally,
also trigger the maintenance cycle. Default Every 10 minutes minutes The frequency, in minutes, to perform maintenance activities. 举例,保留2小时,清理AA*已确认不需要的Trail文件 PURGEOLDEXTRACTS /ggs/dirdat/AA*、USECHECKPOINTS、MINKEEPHOURS 2 不需要检查是否被需要,只要超出2小时的Trail文件都被删除,除非这个进程只剩下一个文件需要保留 PURGEOLDEXTRACTS /ggs/dirdat/AA*、NOUSECHECKPOINTS、MINKEEPHOURS 2 如下满足Windows规则 PURGEOLDEXTRACTS dirdatAA*, USECHECKPOINTS