Delay in updating table

Question

Most of the time, it takes 1 ms to update myTbl using the sql "where myPrimaryKey = 'A123'".
But, on 2 occasions this week, it took 522 ms and 242 ms.
Below is the index fragmentation on myTbl on the 2 days that the delay occurred.
In other days, I see avg_fragmentation_in_percent of PK__myTbl reached 96.969, but I don't see the delay in updating myTbl.
If the avg_fragmentation_in_percent is high (like > 90%), will I see delay in all update, or just occassionally ?
Thank you
index_id name              avg_fragmentation_in_percent    fragment_count   avg_fragment_size_in_pages
1            IX_myTbl       17.960088691796                       121                   
3.72727272727273
2            PK__myTbl     97.1428571428571                     35                     
1
index_id name             avg_fragmentation_in_percent      fragment_count   avg_fragment_size_in_pages
1            IX_myTbl       41.0281280310378                     485                     2.12577319587629
2            PK__myTbl     96.7741935483871                     62                      1

Answer 1

Thank you for your reply.
My sql statement is something like
Update myTbl SET col1 = '', col2 = ''...WHERE myPrimaryKey = 'A123'"
Below are the page count.
Are these numbers considered less page counts ?
index_id name         avg_fragmentation_in_percent   fragment_count    avg_fragment_size_in_pages   page_count
1           IX_myTbl    17.960088691796                    121                     
3.72727272727273                451
2           PK__myTbl  97.1428571428571                  35                       
1                                          35
index_id name          avg_fragmentation_in_percent   fragment_count   avg_fragment_size_in_pages   page_count
1           IX_myTbl    41.0281280310378                   485                     2.12577319587629                
1031
2           PK__myTbl  96.7741935483871                   62                     
1                                            62
The primary is Non Clustered indexed, but it is a varchar(50) column.
When I perform the Update statement, this is the logical and physical read on the 2 databases that had the delay:
Table 'myTbl'. Scan count 0, logical reads 12, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'myTbl'. Scan count 0, logical reads 5, physical reads 1, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'myTbl'. Scan count 0, logical reads 14, physical reads 2, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.