检查各个dbspaces的空间使用状况：
select name dbspace,sum(chksize) allocated,sum(nfree) free,
round(((sum(chksize)-sum(nfree))/sum(chksize))*100)||"%" pcused
form sysdbspaces d,syschunks c
where d.dbsnum=c.dbsnum group by name order by 4 desc
剩余空间肯定是越大越好了
显示各个dbspaces的I/O状况：
select d.name,fname path_name,sum(pagesread) diskreads,sum(pageswritten) diskwrites
from syschkio c,syschunks k,sysdbspaces d
where d.dbsnum=k.dbsnum and k.chknum=c.chunknum
group by 1,2 order by 3 desc
根据各个dbspaces的I/O来调整表的布局，使整个系统I/O均衡
检查哪个表具有最多的磁盘I/0：
select dbsname, tabname, (isreads + pagreads) diskreads, (iswrites + pagwrites) diskwrites
from sysptprof
order by 3 desc,4 desc
同上。
检查表的extent的分布状况：
select t.tabname, count(*) num_ext
from sysextents e, npmdb:systables t
where e.tabname=t.tabname
and dbsname = "npmdb"
and t.tabname not like "sys%"
group by 1
having count(*) > 1
order by 2 desc
表的extent建议最大不超过30个，如果太大，就需要重建表修改extent size的大小从而修改extent的数量
检查表中索引的层数（越少越好）：
select idxname, levels from sysindexes order by 2 desc
检查命中率不高的索引(nrows和unique越接近越好）：
select tabname, idxname, nrows, nunique
from systables t, sysindexes I
where t.tabid =i.tabid and t.tabid > 99
and nrows > 0 and nunique > 0
当索引的效率不高的时候，需要根据实际情况修改
看数据库里面那些表的碎片比较多（碎片小比较好）
select dbsname , tabname ,count(*), sum(size)
from sysextents
group by 1,2
order by 3 desc;
表和索引的读写情况，(考查那个数据库实体读写比较多)
select dbsname, tabname, (isreads + pagreads) diskreads, (iswrites + pagwrites)
diskwrites
from sysptprof
order by 3 desc, 4 desc
那些表的锁竞争比较厉害(越小越好)
select a.tabname,nrows,lockwts,deadlks
from sysmaster:sysptprof a,systables b
where a.tabname=b.tabname and lockwts>0
and a.dbsname = 库名
and b.tabid >= 100
order by tabname;
表的顺序扫描数（OLTP系统的话，大表的顺序扫描数越小越好）
select a.tabname,nrows,seqscans
from sysmaster:sysptprof a,systables b
where a.tabname=b.tabname and seqscans>0
and a.dbsname = '库名'
and b.tabid>=100
order by tabname;
