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.Figure 8.26SummaryReferences[1] Execution Time LimitsETX 102 60-1026 Uen© Ericsson Telecom 1997[2] Software Reliability Handbook, Edition 4EN/LZG 205 603© Ericsson Telecom 1996[3] Plex-C 1 (course book)especially Chapter 6, Block InteractionEN/LZT 101 1279 R4B© Ericsson Telecom 1996[4] Limitations in Signal/Event SendingETX 102 60-1207 Uen© Ericsson Telecom 1996160 Job Execution[5] Selection of Signalling LevelETX 102 60-1116 Uen (was: XT/UD 81 021)© Ericsson Telecom 1997[6] APZ 21, 8.x; 1993 - 1996, A PresentationUAB/B/X-96:068 UenEricsson Utvecklings AB 1996161 Plex-C 2162 Chapter 9 Size AlterationIntroductionMost Plex-C programs use files of records.If the number of records in thefile is alterable, the programs need a section for size alteration.Size altera-tion is always initiated by an exchange technician.This chapter describessize alteration from an operation and maintenance point of view, as well asits implementation in Plex-C programs.Chapter ObjectivesAfter completing this chapter, you are able to:" Describe local and global size alteration events" Apply the signals associated with size alteration" Implement size alteration events in hardware-owning and software-only blocksFigure 9.1Chapter ObjectivesFile SizeThe file size is the number of records in a file.The file size can be fixed oralterable.FIXED FILE SIZE ALTERABLE FILE SIZEno change of file size change file size in program sectorwith size alteration eventsset file size in data sector set initial file size in data sectorusing local number symbol using 0 (zero) or minimum file sizeexample: example:SIZE OF DATARECORD = SIZE OF DATARECORD = 0;ZINDNUM; CINDNUM = 0;Figure 9.2Fixed and alterable file sizes163 Plex-C 2Fixed size files of records store the number of records in a local numbersymbol such as ZINDNUM.Alterable size files of records store thenumber of records in a DS RELOAD variable such as CINDNUM.Thestring indnum is a twisted acronym for number of individuals.VariableCINDNUM is RELOAD-marked, because only the exchange technicianmay increase or decrease the file size.Need for Size AlterationHardware-owning blocks usually have one record per telephony device orother pieces of equipment, while software-only blocks assign one record toeach subscriber, call attempt or route.At initial loading, the operation and maintenance staff need to set thenumber of records equal to the number of available devices in theexchange.Later, when adding or removing devices, or when the exchangeneeds more or less traffic-handling capacity, the exchange technician canlower or raise the number of records accordingly.Figure 9.3 lists positive and negative aspects of file size alteration.ADVANTAGES DISADVANTAGESgood memory economy: reserve inconvenient to the operator: has toonly as many records as needed check, increase and decrease filescorrect dimensioning: assign one SAEs raise the load in the CP andrecord to one item or device are difficult to administerSAE programs are difficult to writeand a common source for errorsFigure 9.3Pros and cons of size alterationIf possible avoid alterable file sizes.Reference [4] contains the followingdesign rule.164 Size Alteration" Avoid SAEs as far as possible.Other solutions such as fixed filesize and sharing an existing SAE must be considered beforechoosing an SAE." Declare a file with fixed size, if the maximum file size is less than50 kW, word-length 16 bits." When deciding for a fixed file size, choose a safe number ofrecords.In other words, the file should have enough records to becongestion-free in all applications.Figure 9.4Design rule for size alterationIf the file size does not vary very much, say +/ 20 percent, use a fixed filesize even if some memory in the DS is wasted.Reducing the CP load ismore important here.Global and Local Size Alteration EventsThere are two types of size alteration events." Global size alteration events change one or several files in one orseveral blocks.Global SAEs allow to combine several filesbelonging to the same function in several blocks." With global SAEs, the exchange technician does not have to adaptthe size of each file separately." Local size alteration events change one or several files in oneblock only.To identify one local SAE, the exchange technicianspecifies the block name and the SAE number which only helps todistinguish different files in a block." With local SAEs, the exchange technician knows exactly whichblock is affected.Figure 9.5Local versus global SAEAs Figure 9.5 reflects, most exchange technicians find global SAEs easierto use, since the staff does not need to worry about block names [ Pobierz caÅ‚ość w formacie PDF ]