gpinitsystem时，提示删除“gpsegcreate.sh_backout.*”失败：

snippet.bash

20200530:16:22:25:2010621 gpinitsystem:test-4:gpadmin-[INFO]:-Deleting distributed backout files
/bin/rm: cannot remove ‘/tmp/gpsegcreate.sh_backout.2111154’: Operation not permitted
/bin/rm: cannot remove ‘/tmp/gpsegcreate.sh_backout.2111167’: Operation not permitted

原因是其它用户的残留文件/tmp/gpsegcreate.sh_backout.*文件，当前用户无权限删除，所以手动删除这些文件后，再重试：

snippet.bash

sudo rm -rf /tmp/gpsegcreate.sh_backout.*

gpinitsystem阶段，莫名其妙的失败，安装日志只是提示有segment安装失败，除此之外没有其它错误：

snippet.bash

20200530:18:38:36:3113385 gpinitsystem:test-4:gpadmin-[INFO]:------------------------------------------------
20200530:18:38:36:3113385 gpinitsystem:test-4:gpadmin-[INFO]:-Parallel process exit status
20200530:18:38:36:3113385 gpinitsystem:test-4:gpadmin-[INFO]:------------------------------------------------
20200530:18:38:36:3113385 gpinitsystem:test-4:gpadmin-[INFO]:-Total processes marked as completed           = 172
20200530:18:38:36:3113385 gpinitsystem:test-4:gpadmin-[INFO]:-Total processes marked as killed              = 0
20200530:18:38:36:3113385 gpinitsystem:test-4:gpadmin-[WARN]:-Total processes marked as failed              = 20 <<<<<
20200530:18:38:36:3113385 gpinitsystem:test-4:gpadmin-[INFO]:------------------------------------------------
20200530:18:38:36:3113385 gpinitsystem:test-4:gpadmin-[FATAL]:-Errors generated from parallel processes
20200530:18:38:36:3113385 gpinitsystem:test-4:gpadmin-[INFO]:-Dumped contents of status file to the log file
20200530:18:38:36:3113385 gpinitsystem:test-4:gpadmin-[INFO]:-Building composite backout file
20200530:18:38:37:3113385 gpinitsystem:test-4:gpadmin-[FATAL]:-Failures detected, see log file /home/gpadmin/gpAdminLogs/gpinitsystem_20200530.log for more detail Script Exiting!

此时，可以尝试gpinitsystem带-m参数，指定安装时的并行度，例如：

snippet.bash

[gpadmin@test-4 ~]$ gpinitsystem -m 25 -c ~/gpinitsystem_config

查询执行过程中报磁盘空间不足：

ERROR: could not write XXX bytes to temporary file: No space left on device

GP查询执行过程中，可能会将查询算子中间结果临时溢出到磁盘，如果GP临时文件所在磁盘空间不足，会导致查询失败。按照上述测试环境，建议为每节点保留200GB磁盘空间。

GP默认参数是大约是按照10个并发场景配置的典型值。大内存环境，对于单个事务的OLTP性能测试，GP的默认参数偏小。建议调整相关参数。

一个事务的单条查询语句在一个segment上，可以使用的最大内存量。

一个事务的单条查询语句在一个节点的所有segment上，可以使用的最大内存量。属于一条查询可以使用的内存上限，是对statement_mem的保护。

有些执行失败，报以下VM（虚拟内存）错误。该参数是单个segment可以使用的VM大小，可以根据本地总内存大小和segment数调整配置。

snippet.bash

ERROR:  Out of memory  (seg3 slice4 10.10.0.4:6348 pid=3535218)
DETAIL:  VM protect failed to allocate 8388616 bytes from system, VM Protect 7335 MB available

官方文档关于此参数的说明：“the amount of memory (in number of MBs) that all postgres processes of an active segment instance can consume.”

使用以下方法修改，并重启GP集群：

snippet.bash

gpconfig -c gp_vmem_protect_limit -v 8192
gpstop -r -a

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